So...my FIRST engine seizure occurred during a long, abusive trip. Fortunately it happened near home. I think it happened due to a combination of my naivete and poor oil-mixing technique. You see, it was November...it was cold...and I had the BAD habit of trying to mix the oil IN-TANK. This would result in globs of pure 2-stroke oil fouling the carb initially, and then riding with too little oil in the fuel afterwards...I was a dope. In this case, although the engine siezed, only one ring of the pair was damaged, and the jug-melt was minor. I was able to lightly dremel and buff both the piston and jug-wall and put the bike back in service while I awaited my new rings.
Personally, my first step in this situation would be to remove the jug and assess the damage...I wouldn't try turning it over at all; there is the potential you could make worse what could be a simpler fix. Since you hadn't been using oil, I'm leaning more towards taking the entire engine off the bike and splitting the case to inspect the roller-bearings (as well as the two needle-bearings). The combustion-chamber's roller-bearings are relatively inexpensive, and easy to replace...they're also probably mildly, if not efficiency-killingly damaged. You now also have the specter of potentially damaging debris in the crankcase as well...like a sneaky time-bomb...a tiny chunk of metal could be lurking in there only to loose itself at cruising RPMs and lodge itself comfortably between the cylinder, piston, and ring: KABOOM!
As there was no mention of the proper oil-mix, I suggest that going forward you PREMIX 87 Octane with run-of-the-mill ash-free 2-stroke oil at about 25:1 . I premix my oil 4:1 with hobby-store gumless castor-oil...the type they use in RC planes and cars. It's super cheap, and provides excellent lube and forgiving protection. It also smells nice.
Now, DON'T screw up your _PRE_MIX AGAIN!
Curious: who sold you the engine, how old was it, did the seller ride it, and how many hours was on it?