IMO there might be two answers:
1. some technical problem which the pool owner does not want to tell
2. pool changed its CATc reward address and mine for some hours for itself
Is there any way to verify the second point?
Cant answer point 2, but for 1. it might be more then possible. I dont know in which timezone the pool ops is, so he might be sleeping and his cronjob blockfind just stuck, or did he found blocks again after that 5 hours ?