Subcontractor Puts a Lien on my House

Background - roofing subcontractor has put a $5000 lien on my new-to-us home. We've paid the contractor in full. I only have quote from the contractor, at the time I didn't know he was going to sub out most of work, but he is paid in full. Sub contractor shows up at my place a 2 weeks later says he didn't get paid. I state we've paid - he tells me he can put a lien on my place - which he does. Three thoughts I have, which may or may not be true -1) contractor has no concept of cash flow management and can't pay subs, 2) subs play games with unwitting customers to scare them into paying 3) contractor and subs are both in on the scam. Is the honest homeowner really the victim here? Can anybody help with logical next steps for me? It's a new mortgage so I'm in no hurry. (yes, I know, I know, before anyone chimes in with 'contracting' advice- I should have had a a more formal contract, it was not low-bid). Thanks for reading!