Talk to your manager for clarification.

To get paid for sick time you have to mark it in the Punch Communication page of the DRB.

You are always allowed to take time off for being sick, however if you only earned 5 hours of sick time and take off for an 8 hour shift you can only get paid for the 5 hours of sick time you earned.

If you want to use sick time to cover these shifts (assuming you have some) you’ll have to write it in the book, otherwise it will be unpaid.

As for why the manager didn’t mark you out of the 3rd day, idk. It could be that they found coverage for the first two already and moved those shirts off your schedule and onto someone else’s and they still haven’t covered that last one. Or it could be something else. It would be prudent to ask.