The three options are (a) the feds hold the cash until its origin is found to be legit, (b) they hold the person until the cash is verified legit, (c) the suitcase of cash and the person fly away never to be seen again.
I guess the 4th option would be making it much easier and faster for the DEA to obtain a warrant; but this just leads back to a, b, or c.
n.b. I am totally against local cops holding any amount of discovered money during random searches. That's a huge conflict if interest. I'm mainly commenting on the original post.