The case of the missing caterpillar

To entertain the kitties, we purchased a three pack of caterpillar toys--one grey, one wine-colored and one brown. I think they have catnip inside them to really keep the cats interested. Calvin, our more rambunctious kitten, took a liking to the caterpillar toys. However, the brown one has gone missing. Charles and I have searched in every logical (and a few illogical) places that it could have gone to. The kitties liked hanging out under the couch the first few days we had them, so we looked under there. Calvin likes to go behind some books on the bottom shelf of the bookcase, so we looked behind the books. We looked upstairs in case he carried it up there during the middle of the night. We looked under and behind the chair. We've basically looked everywhere. The caterpillar must have come to live and scurried away. Or Calvin ate it. We're not really sure. The other two caterpillars are still with us, so we may have to enter them into witness protection so they don't meet the same fate of Mr. Brown.