I agree with the other poster that you should really let the attending know that you are interested in their field. Also be enthusiastic and ask questions, but in a respectful manner. I think that if you introduce yourself to the attending at the beginning of the rotation and tell them that you are very interested in this field and would like any feedback on how to improve, etc. then it goes far. Look up articles, find info on guidelines, etc.
I really do think that that attending was doing you a favor when he did not write you a letter. You would be amazed at how many letters I reviewed as faculty at a residency program that were so generic or even downright negative. If I can't write a letter for a med student just because I don't know him/her well-- I am very straightforward about it because if a recommendation letter is not strong then it really is worthless. I agree with the poster that said to get a couple different ones so that your dean can pick the strongest one. Get the letter before the end of the rotation- consider asking for it the first day of your last week and do have a copy of your CV and other info to give to the attending. I think you have more than enough opportunities ahead of you with the rest of your rotations, so don't worry.
nbp wrote: The problem is that, for whatever reason, I haven't really been connecting with my attendings.
I feel like this is a common problem, unless you did months of research or something with the same attending. I'm starting to worry about it, too, since I've been sitting out this whole last year on an LOA....it's been a year since I've worked with any attendings!
Somehow all my class of 2011 classmates made it through, which gives me hope. Thanks for this thread, nbp, and thanks for the advice, everyone.
Another question: is August too late to get a letter? That's when my AI is scheduled, and it's my first 4th year exposure to the field. :/