It is fairly common for attending physicians, in a rec letter, to make note of the amount of time they have spent with a student during a rotation. So, if you've spent two days with an attending and they mention this in the letter, that's not necessarily a bad thing - like I said, it's often a standard thing. What you really need to is evaluate the rest of the letter. Is it really as strong as you think?
Two days is not a lot of time for an attending physician to really learn a lot about a student. Having said that, it all depends on your experience and the way the rotation was set up. You can knock the socks off an attending in two days, especially if you spend considerable time with him or her and perform at a high level.
Samir Desai, MD