Question about dream recall

[TheShins]

For the past week or so since I've read about LDs, my dream recall has been increased greatly from 2-3 dreams a night. Last night though, i went to bed later then normal, around 11:50 is probably when i fell asleep. I woke up at 7:10, which is almost exactly 7 and a half hours after i fell asleep, but I couldn't remember any dreams. Could this be because I was tired from a different sleep schedule? Thanks, Bobby