Sure, maybe the recruiter/company messed up on the contract side of things...but at the end of the day the recruiter found a candidate that the company likes and the company isn't willing to compensate the recruiter for his efforts.

Let's look at a similar but slightly different scenario - If there was an issue with your contract and the company realized they didn't have to pay you...you can guess what decision they're probably making.

Sure, while this might not be illegal (and you wouldn't be at any fault either way), I definitely wouldn't want to work at a company that operates this way.

Also, not to mention - the recruiter will probably find out you got the job, when you update your LinkedIn, you post something online, etc...