1. Wash the item again, and try harder, using, uh, thought-waves.
2. Ignore the problem. After all, the item likely belongs to one of the kids, and do they care? No.
3. Throw it out.
But, evidently I’ve been completely missing a fourth option: stain removers! Where have I been? Dan Crane at Slate recently did some home testing of various stain-removal methods(including the option of “nothing”, clearly a man after my own heart!) and wrote a nice wrap-up which is well worth a read even if simply for its humor. If you just want the down and dirty, I’ll summarize: most commercial stain removers are pretty useless, but Zout seems to be the best of the bunch.
And me? Okay, I sort of lied up above. I do have stain remover that I use when I happen to think about it: Sonett gall soap. It’s European, does that make it better? I know it works pretty well. I have the bar version rather than this one. Ooh, and it contains “bovine gall”. As in gall bladder. Makes you want to try it, doesn’t it? Who was the first to discover that it works on stains, I wonder? Um, not sure I want to know the thought process in that one.