I tend to be somewhat meticulous (and occasionally anal) as to stains on newly purchased items of clothing. I recently purchased a new pair of Diesel sneakers (white leather) and, brilliantly, wore them out this weekend to arguably the worst place to wear new footwear that you don't want ruined (I was in New Orleans for the weekend, and I wore them out on Bourbon St. one night). Shockingly, given how immaculate and spotless Bourbon St. is on an average Saturday night, I stumbled home to find a giant, dark smudge on the white leather. Usually, I'm fairly proficient at removing stains, but this thing (some unidentified mix, I presume, of various alcoholic beverages, bodily fluids, and various sludge-like components of unknown origin) won't respond to anything I've tried. Does anyone have any particular tips/tricks/product recommendations to remedy the situation? Thanks in advance.