I let the pups out a little after 10, and Mochi came back in limping. She is a shrieker, anyway, so it's hard to tell if she was bitten or stung by something, but her paw was definitely in some pain. Looked repeatedly at her paw with a flashlight and found no injury. To say I'm distressed is to understate. Fingers crossed she'll be okay, but most likely vetting in the morning. :(
Morning update: I have a flouncy-bouncy pup once again. Whew!