Back when I was a lot younger, I used to do bookings for several clubs around my home town, so this is meant to be a look at your situation from the standpoint of the persons that hired you.

Clubs or organizations pretty well know what will appeal to their patrons. That's why they would hire people like me to find entertainer(s) that meet certain criteria. If they asked for a trio that is what they expected. In reality, the contract was canceled when you could not provide the trio. So you had two choices. (1) forget that gig entirely, and maybe suggest someone who they could contact in short notice, or (2) sell yourself as a solo replacement. You choose #2, and that is perfectly proper.

If you had never before performed as a duo, you had absolutely no right to expect them to hire a duo. Clubs hire you not because you are nice folks, but because they want to make money.

Get as far away from those other two as you can.