I do think Alan would think Flynn was alive and grab on to the idea that he was in the Grid. Alan's never accepted the idea that Flynn is dead. And he just got a page. He probably would think it was from Flynn (whose rampant irresponsibility got him trapped inside), I think. But I agree he would not accidentally digitize himself and I don't think he'd do it intentionally, either. At least, not immediately. He wouldn't want to end up like Flynn, after all. And he wouldn't want to leave his loved ones wondering the way Flynn did if he couldn't get back. Now, whether or not he's married to Lora (depending on whether extra-movie material counts), it would be very logical to get in touch with her or with Gibbs (if he's still living and of sound mind) as they would be the only experts he could find on the technology. Really, from his perspective, if Gibbs or Lora could just just enter the "undigitize" instruction on the keyboard (after verifying data integrity), then that's the safest and best thing to do (though it doesn't make for much of a movie). He'd want to tell Sam what he'd discovered, though, before doing anything else.
I'm still not entirely sure what Alan thinks of the page. Or Flynn being gone, for that matter. He never comes out and says he thinks Flynn's not dead. He admits to Sam that he doesn't think Flynn would have deliberately left Sam, but of course, being dead is a good excuse to leave someone not-on-purpose; he seems more to be countering Sam's insinuation that his dad just walked out on him.
And as I've said before (probably about a billion times), Alan and the pager confuses me. He sleeps with this thing because he thinks it's so important, BUT when he does get a page, he waits until the next day to do anything about it and then all he does with it is pass the info off to Sam, hoping Sam might investigate it... some time... perhaps. That's not really something you do if you truly believe that your friend is still somewhere to send you an urgent page on which you will need to act immediately. For that matter, if you have hope you'll still hear from him, why disconnect the phone line from which you will hear? (I am dying to know what instructions Flynn gave Alan with the pager. Should he call the police? Come to the arcade? Read a special set of instructions Flynn will leave somewhere for him that will explain everything and detail how he should help?) And even if he assumed Flynn got into trouble, why would he take 20 years to ring Alan up about it?
I've always sort of wondered if he doesn't just use it as an excuse to light a fire under Sam's ass. "Send him to the arcade, maybe he'll get nostalgic and decide to help me out after all." After all (as I've also said before), what does he expect Sam to find there that trained forensic investigators, and no doubt Alan himself, never found?
Unfortunately, this is one of those things they sort of expect to give to us and we're supposed to take it at face value without thinking about it too hard or asking questions. And this one's a big one for that.
(Although: what didn't occur to me before, is my assumption that Alan isn't familiar with digitization of living beings and therefore wouldn't have reason to think Flynn would survive digitization. After all, an orange is matter but it has no sentience... and he might not know how a laser would transfer sentience or if it would. But, we also don't know how far Encom went with digitization [nor do we have confirmation that the project isn't still going on even in 2010], so it's possible that in the years since T82
, they've possibly moved on to live animal subjects or something, and would find out that you can transfer a sentient being into the computer and have it come out still alive.)
I'm not sure, either, how much Clu knew about the pager. Did he know who it would call and why? How does Flynn make contact with it from inside? And where did Clu obtain the knowledge of how to do that/a device that might do it/whatever? Did he get it from Flynn, as in steal it? Or is it something Flynn also gave him, as a safeguard-- "if something happens to me in here, do this to contact someone on the outside"? Does he know it connects to Alan? Does he know it connects to anyone? Did he think it would bring someone in, or was it just a stab in the dark to see what happened, if anything, and whether whatever happened might be able to help him out somehow?
Argh. Should have been a much longer film; there is so much that really should've been explained better, but they didn't have time, so they just sort of, as above, threw it at us half-baked and hoped we wouldn't look too close.