My site disappeared from SERP

That's your answer there. I was assuming that was the case, but wanted to make sure.

here is the issue, sometimes Google ranks new sites (and new pages) high in google (like on page 1 or 2) right out of the gates solely due to "freshness".

That is, if I put up a new site and it ranks well out of the gate, I shouldn't assume that the site really is worthy of that ranking in Google's eyes. it is merely google putting a new site up high. It happens all the times and I would say the majority of my sites have this happen to them. Sometimes new sites can bounce new sites can bounce around crazily. I've had a new site show up on page 1 in the first week, and then to be around #200 for awhile. With adequate backlinks, it all works out in the end.

Then, you start adding backlinks and the site shoots back as Google re-evaluates the true worth of the site. Unfortunately, that is just the nature of the beat. Just keep on building backlinks, and don't assume that Google really thought your site deserved that placement. View it instead as a quick little glimpse into the hopeful future of your site after you build more backlinks to it.

Tom