Too much work to do real flowchart in ascii, alternative version:
Are they incorporated?
-> No: sue founders personally
-> Yes:
-> Will they go under in < 6 months?
-> Yes: your money is lost
-> No:
-> Do they have assets?
-> No: Your money is lost
-> Yes: sue asap
Alternative: some companies buy debt at a discount. Some collections agencies do it, since they're in the business of chasing debtors already anyway. Not sure in US who would do that.Do not do anything to website or whatever else you still have access to.
Those are pretty much your options. You seem to have some ideas of yourself (judging from you mentioning 'YC', 'access to code', etc.). Those are all bad, ineffective, stupid - or all three courses of action.