I took a capsule in a blister pack, (easy to open, with a yellow pull tab) it was gray with plum or purple from a preschooler

. It had no marks, letters or signs on the pill or the pack. Please help, mom stated it was it was not hers, so I really need help to identify, because next step is to turn over to police, and I really don't want to have a preschooler or his mom arrested for drug possession if it is just a simple misunderstanding or if it came from a staff members purse. We keep them locked up but it could have fallen out... please any help..
Thanks