Ah, memories...an abandoned trailer...what a pita.
Check Ohio law/lawyer for possessory liens. You can't hold the trailer hostage (that's a whole 'nother episode on Redneck Round Up) but you might be able to get lot rent until it's moved off your land. When our tenants abandoned their trailer, a possessory lien against the finance company was an option.
You'll have to file suit against the previous owner for back rent. It's not the finance company's problem that your tenants were irresponsible.