If I look around my house, there are many items that are really my parents (and maybe even my grandparents) stuff. It could be a tool (like the wooden tap hammer in my tool box),or a kitchen item (the apple pairing knife), a blanket, tie, the list goes on and on. Since Jenna has left for college various items have disappeared (forks, garden tools, etc.). It is a natural occurrence that functional stuff begins to disappear. Some of these treasures create instant memories of past projects and places lived.
I'm sure there were times when Dad would be helping me on a project here in Cincinnati only to discover his tool in my tool box available for use. "I seem to recognize that hammer, Garen". My response - "Oh Yeah, I must have borrowed it, isn't it great to have a familiar tool to work with here in Cincinnati :). Do you need it back? Great - I'll just keep it here for future projects."
The best part of parental stuff disappearing (as a parent) is having someone to blame when you can't find the item in the endless stuff that accumulates at home. "Where did I put that pair of pliers? Jenna must have borrowed them."
Whether borrowed (by your kids) or misplaced - the second best part is being able to replace Dad's stuff (that I "borrowed") with a new tool.