It seems that the Plumber did his job, after all it was a flat fee. But what a professional should have done was at least asked if you had a bucket or something to clean it up with. Or being a plumber he should have had something to clean it up with, it would only make for better business. The plumber could of been very busy that day, or had some type of family issue that required he get done fast on that particular day. The point is, it would have been nice for him to clean the mess, but unless it was in a contract, then he is not obligated to. In my experience people are willing to clean up or cut certain nice-ety's in order to save money. It could have been a number of things, If he did the job, and it has worked fine since, then I would most likely rate him as an A, but in a future note put ask about cleanup if desired. Thanks, there are always two sides, and I would've at least attempted to clean a little.

It could have been a bigger mess, that he cleaned up all except what you saw left. I wouldn't judge him on something you didn't ask him about.
Saint Contracting Company Inc.
SaintContracting.com
Mold Remediation
Restoration
Remodeling
Building