A moral dilemma of minor proportions

Once or twice per year, I find myself in an unexpected situation where I'm forced to rethink my reasons for giving up meat. The situation usually goes something like this: I'm at a restaurant by myself, and I ordered what I thought was a meat-free dish, but when it arrives — lo and behold — 'tis not what I expected. Sometimes it's my fault, like when I neglected to fully read the menu, and I casually assumed there would be no meat in the "vegetable soup". Sometimes the restaurant staff simply goofs up the order. But whatever the cause, I am now faced with a minor moral dilemma: sending back the dish might actually be worse than just eating it.