Yep. Even LJ rocked up last week apparently looking like death, but he still turned up expecting to play. That was one time they did just say "No".
I got the flu earlier in the year, felt a bit crap one day, went to bed, woke up and felt absolutely fine. Went to the gym, after 10 minutes all my energy was completely gone and i went downhill from there. Could've been the same with Beamer... thought he was 100% but wasn't. Who knows.