Katie, quick question.
Why am I getting one of my "CYA" moments about this situation?
If I didn't know that I was exhausted (emigration organisation etc meant I only had about 1.5hrs sleep last night!), I would say that your boss should be made aware that there could be possible repeat behaviours over future 'bookings' from these guys! It is not singing your own praises, it is letting him/her know that someone was trying to walk all over that particular group of training attendees to suit the trainer's own possible inefficiencies/dis-organisation!
Just my hunch however, but only you really know how the land lies with your work!
Jess
