I'm going to keep some info on location and names vague, as it is not the point here
I am playing in a B&M satellite to qualify for an event, two seats are available, seven players left. Again, immaterial which establishment,which event for the purposes of this post
I'm in seat 8, one of the short stacks
Seat 7 is the short stack
Seat 9 is chipped up.
Seats 5,7,9 have entered the competition together
Seats 1,2,4 have entered the competition together
I have objected to seats 5 and 9 talking another language at the table. On objecting, I have been accused of being a racist, but the card room supervisor has backed me up
Seat 7 limps into an unopened pot on the button
I pass
Seat 9 checks
Flop
tc kh qd
Check check
Turn

Check check
River

BB checks, button moves all in for last 2300 into a pot 4000 (800-1600 blinds, a 1600 limper)
BB immediately passes
Button proudly shows

BB roars with laughter, says "well played" and displays td th. He's checked trips twice to a short stack and passed getting 4-1 on the end
I immediately complain, pointing out that this is the most blatant example of softplay I have ever seen, that it was a disgrace and an insult to the other players
I explain the situation to the supervisor who says there is nothing he can do but he will watch the final table from then on
By now it's really kicking off, Seats 1,2 and 4 aren't experienced live players, they are looking bemused. Seat 5 is asking me" Are you saying my friend is a cheat" (er, yes), Seat 9 says "I was waiting for him to bet and on the river I thought he must be betting with a straight"
I reply "It is either soft play or you are the worst player I have ever seen to check a set twice against a short stack. I don't care who he is, to be fair to everyone else you have to try and win the pot here"
At that point, frankly fuming and upset ( it takes an awful lot to make me lose any control, far too placid and good natured, it's a downfall of mine!!!) , I got up, left my chips there and went home. Maybe I shouldn't have done but I'm comfortable with my decision, some things are more important than a game of poker. Principles, for example.
Here's what I want to know:
Is there a prima facie case to suspect softplay here?
If presented with strong grounds to suspect softplay, what can a cardroom supervisor do?
Would you have handled this any different if you were me? (I DON'T want to be told I should have stayed and played, I know I let them win, but that was choice)
I am writing formally to various people to request that my initial buy in is returned. Do I have any case for this? Should I complain about the supervisor?