There was a nasty bug inside the teabag
If you find something in your drink, it was probably in the cup before you poured the liquid, or it flew inside it afterward. This person found out there was a third reason for it.
It came inside the teabag. The good news is that they did not run the risk of swallowing down the creature since it was safe inside the bag. The bad news is that drinking “spider tea” does not sound very appetizing.