Yes, you absolutely can win these cases, but you must have essentially air tight evidence as to where the money came from and that was in fact the money that was seized. You can also appeal any judgement which prevents the money from leaving custody until the appeal is complete.

The chances are very small due to the way the case is structured but it is entirely possible and it has been known to occur. The main issue is it's a _civil_ case against property and the rules of a civil trial massively over benefit the government and effectively ignore fourth amendment property rights.