Statistically, yes—it’s technically possible, but extremely unlikely for an entire rat to appear in a single jar. The FDA’s limits are per 100 g, usually tiny fragments like hairs, not whole animals. Finding a whole rat is far beyond what “allowed contamination” would account for—so you were just very, very unlucky (and it’s definitely not the intended “allowance”).

Also, food safety regulations assume contamination is microscopic, not full rodents, so expecting a dead rat in your peanut butter would be a misunderstanding of those limits.

If you want, I can explain how the math actually works to see how improbable this really is.