Take a vacation toy inventory
Smart travel planning, from Duane:
Going on vacation? If the kids are planning to bring more than 1-2 toys, then set up a space for them to "pack" their toys just like you pack your clothes and supplies (even if it's just a particular pile of toys on the floor). Then, take toy inventory and make a list of all the toys they put in the pile. After a few days in a strange hotel (or house) playing with them, the small toys tend to end up everywhere. When it's time to go home, rather than uttering "Now, are you SURE you've got all your toys?" 57 times, you can go through the list and make sure everything's accounted for.
Do you have a trick for keeping track of toys while on vacation?