The same thing happened to my Black 96GT last summer...
I live in a fourplex. My neighbor, whose garage is right next to mine with just a thin wall seperating them, was painting his white truck in his garage.
Well, I go out and open my garage door later, and it just reaks of paint fumes in there. There was a white dusting over my whole car.

...let me tell you, he was out in the driveway for several hours polishing the sh*t outta my car. It did all come off though. Lucky for him.
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T-Bones 1997 Cobra#6342 born 6-11-97
Wht/blk, Pro 5.0,FRPP 4.10's, aluminum driveshaft, FRPP throttle body, C&L 80mm MAF, K&N, Steeda U/D pulleys, Steeda timing adjuster, Flowmasters, s/f connectors, FRPP pro springs, BBK caster/cambers.
My old 96GT