catch (one) at a bad time
To encounter or try to communicate or work with someone at an inopportune time, such as when they are busy or preoccupied. I'll definitely help you with that report later—you just happened to catch me at a bad time right now. If Dean was grumpy, you probably just caught him at a bad time.
catch someone at a bad time
to attempt to speak or deal with someone at a time inconvenient for that person. I'm sorry. You look busy. Did I catch you at a bad time?