well i dont think your gonna have any other choice other than wipe off the mess and start over, the stain should have been put down first then the finish..to wipe it off you can use mineral spirits and to get the majority of it off then go back with some steel wool to get in the crevices better then do a wash coat of mineral spirits see what color he has then if he wants it darker then restain to desired color and apply the final finish..i am not a pro at this but i have co worker that was..
if i were you i would contact a pro in your area to get his opinion and maybe there is a easier method than the old way of doing it..
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