So, a transit card is

It wasn't like the passport where you carry it and it's a one-time use, so I guess the transit card was also in my bag for some reason because it wasn't a one-time use either. I didn't feel much effect & didn't really understand it, so I haven't bought one now, but I'm relieved to know that the one left in my bag wasn't a random consumption item but could be used multiple times.