Hello, I had a short time ago (3-4 days) the chance to loot the mascot Ms.madeleine but, yesterday by wanting to “equip it” as a mascot for my witch doctor she was no longer in my list of mascot.
If you can not return it to me it is not very serious, I wanted especially to report you bug.
Have a good day 
Is it possible that you right-clicked it to send it to your Collection with your Stash open? If so, it is probably somewhere in your Stash. If you find it, make sure you right-click it with your Stash closed. (Only your Inventory should be open).