Personally, knowing that you were due to do it the next day, I would not have phoned them and turned up and started cleaning. After all if your mate had not seen the "others" you would not have known.
If they had come out and stopped you, you could have referred them to your written agreement and still invoiced them.
If they didn't stop you, you could have just invoiced as normal.
Of course if you have no agreement in writing, which is unusual on commercial work, then although ignorant of them not to inform you, there is probably no comeback for you.
A written agreement/contract, can be broken as easily as not having one, but at least it does give you some weight especially if you have cancellation terms within