Confused about upcoming FET lining check

Looking for some help since it’s a holiday weekend and I’m having a hard time getting a hold of my doctor because this isn’t an emergency.

I am preparing for FET. Went off of birth control on Sunday May 19th and started estrogen patches, per my Doctor’s direction, on Tuesday. I just got my period today. I’m supposed to go in for a lining check on Friday the 31st but if I’ve only been done with my period for a couple of days at that point will there even be a lining yet? Has anyone experienced anything like this before?