Period Sex: Worried/Confused

Today's the last day of my period .. I always wear tampons.. Earlier today, I met up with  my boyfriend and things began to escalate. I warned him that I was on my period (although it was extremely light, since it was my last day) but he didn't seem to care ...

Next thing I know his cock is inside of me, penetrating me

It isn't until afterwards that I remembered I had a tampon in and was confused as to what happened to it. I certainly did not feel him remove it.. I felt no pain during our affair and continue to feel nothing. I looked around his car just to double check that it wasn't removed somehow .. I've heard plenty of ladies on here say that tampon in + sex = no bueno .... I inserted a finger in my vag, a couple of hours ago, to check if I feel my tampon string but I felt and continue to feel nothing...

Not sure what to do .... Do you ladies have any advice for me???