How can this be? I would be upset too. I’ve seen it happen a couple times and being in ministry myself, I usually make sure that I speak to the Lector who read the wrong one after Mass, because I know them all as friends. Usually it’s a turn of the page.
Now, sometimes there is a choice of a couple readings for any of them, but that is rare except at Christmas and Easter. Some priests prefer specific readings then.
Do you have a Lector Coordinator? If so, ask them what is going on too. They should all have assignments and practice booklets. We do.
The process is simple: know the date, look at the missal which tells what day of the season we are celebrating, make sure that the Lectionary is set correctly before Mass. I bet some Solemnities that fall on a Sunday really confuses them, especially if they can’t get Ordinary Time right!
Fortunately we have a deacon at all our Masses and if I don’t, they set the Lectionary with ribbons correctly.
Question: How off are they in proximity to the date of the “real readings?”
Suggestion: This weekend, before Mass with missal in hand, go up to the Lector and simply ask, “this is the 16th Sunday in Ordinary Time, right?” I would be curious as to what reaction you would get and if he/she checks the Lectionary then. LOL!