Yes, this is actually a common way of getting out of debt. Often times the "proof" for a debt is lost in the tangled web of debt collection, and by the time someone comes around to collect, there's no tangible evidence the debt was valid.

It's a best practice to request proof of any outstanding debt before paying collections, and I've personally seen cases where friends have gotten out of a debt that went to collections simply by asking for proof, and when it wasn't provided, poof it went away.

I'm a sucker, and don't take advantage of this, but I don't blame anyone who does. Keep good records, and it won't be a problem!