Lost domain name on several money makers.. Now what?

Feel really dumb and I'm sure many people have gone true this. Long story short I stopped working on several sites that we're making me money to focus on product development on another idea. These were the niche style Adsense type of sites that beginners love to start with because they have $$$ in their eyes. I somehow forgot to renew the domain name! Lol

I was lucky enough to be part of the few that earned money from this stuff but I got lazy. It's been 2-4 months since the name dropped and google shows no clues of their previous existence.

I mention that because I hardly do back linking on these sites so I don't have a problem starting over with that. So here are my options..

1. Contact the new owner and hope he doesn't rape me

2. Somehow get the site running on new domain and fix link structure. Could be done since site wasn't branded with .com or anything so I can buy .net can this even be done?

3. It was only averaging 300-400 month anyways continue focusing on product development

What do you think? Any advice? I don't really care for the niche type of business model but I feel like I put enough effort into learning and building to not just give up on these sites.