first off,
NOOOOOO
you didn't even check his milage or check your oil before you left? or told him it leaked?
i almost want to advise you not to even bother him.
if he seems like a well manord person then dont even bother with his bs and find a runnin ge and swap "when you find out for sure it's total damage of course"
i've only let my best friend of 15 years drive my car only a few times.
my gf once down the block to the store where she seemed to exceed 70mph with out a problem.. (gte BPU++ W/ auto)
i just dont let any one drive my car, with exception to my brother since i drive his mkiii more then he drive's mine, though im the mechanic, and have fixed/ will fix what i break and any problems that occure.
if you do bother him, i would ask him when , and what conditions "if" he noticed the miss, and so on,
possibly he went through a puddle or so forth and likely wasn't at fault.
i would hate to hear he was a kid, or some one under 50 that possible has never driven a supra before...
just for aspect, my friend from high school will not let me drive his 82 n/a mkii while i have 3 turbo mkiii's and a turbo mkii.