Thumbtack in my Shoe

My team lead was like "Okay guys! Throw your shoes into the middle of the floor! It's No Shoes Day!" She kicked her foot, sending her flip-flop sailing a few feet to the land in the middle of our aisle of cubicles. Three girls followed suit. I was wearing Converse and bent to untie mine to add to the pile, but I told her I was concerned I might step on a thumbtack and get tetanus. She scoffed at my worries and commanded I remove my shoes, and who was I to argue? About an hour later the staff leader walked by and said "What the heck!" at our pile of shoes but didn't make us put them back on. Another hour later my foot was getting cold so I put my shoes back on. Fast forward to later at night, I'm walking on the sidewalk and my shoe isn't going down flat because there's something stuck to the bottom of it. I'd noticed it intermittently throughout the day but hadn't given it much thought. I got to my sister's apartment and sat down to check the bottom of my shoe and lo and behold! it was a purple star-shaped tack that had been on the wall of my cubicle. At some point during the day I'd stepped on it at work. Luckily it was when my shoes were on and it did not give me tetanus. I just want all you people to know I'm not paranoid, but instead rightfully cautious. These things can happen.