Three questions off the top of my head:
What does an engine-vacuum gauge tell you while the problem is occurring?
Was the compression test held for a time on each cylinder to watch for bleed-down, and if so, what does *that* reading look like on each one?
Those two are looking for something mechanically damaged, like a marginal gasket or a warped head. But as long as you're underhood: is On-Board Diagnostics II showing any trouble codes? (As if you'd cooked a sensor somewhere? )
Free bonus question, assuming this is port fuel injected: are the injectors all happy?
Also: any exhaust gases in the coolant? any coolant in the oil?
Now for the good news: from the symptoms you described, and most importantly the things others mentioned that you considered and cleared, I am not really guessing that you ruined the engine; we're probably looking for more subtle things. Close escape!
--Joe