@Anonymous4,
Look, only you can really answer that. But you should consider a few things.
* Blaming alcohol doesn't cut it. I'm not saying that you had full control of your faculties but I take it you weren't completely slobbery falling-down drunk. Most women (unless they're pros) don't give their numbers to guys who are essentially puking themselves.
* What's your overall feeling about all of this? Relief that you realized you had the number and then quickly excised it before things could go any further? Fear that your fiancée would find out? Regret that this didn't happen before you became engaged?
* How do you feel about marriage in general? I don't mean the wedding. I mean marriage. Do you see being with this woman when she's pregnant? Sick with cancer? Obese? Old? Not all of these things happen, of course - but can you see those things as happening? Or are they dealbreakers, any of them?
* I don't really think that anyone is "perfect" for anyone else, at least not over time. Mr. j and I don't see eye to eye on everything, but we get along well, we are considerate of each other and we try not to hurt each other. Plus we don't feel threatened when the other one seeks friends (even if they're of the opposite sex) to fill in missing things, so long as those things aren't sexual. What I mean is, I'm on a strict diet. My husband is not. I spend time online on a diet website. Lots of time. I have male and female friends there. I don't talk protein and steps walked with my husband; I talk about it with those people. My husband is not threatened by this; this is just something that I do, and that interests me, but he doesn't do it. It's a place where he's not "perfect" for me - but it doesn't matter.
* BTW, how would you feel if your fiancée found out about this escapade? How would you feel after you deleted the #? Before? And how would she feel?