Oh my. This seems to be a real problem for all of us. NO, you are not being too picky!!
I have to constantly stay on my housekeepers about things. And I do mean ALL the time. I talk to her EVERY WEEK.
One thing I did, that seems to have helped: When I send my Thank You email to each guest I include a short Comment Sheet that asks them to rate the level of cleanliness of our home.
My guests know I am not nearby, and they all understand that I want and need to hear their feedback on matters. Most are happy to share their comments. ( I think it makes them feel as if they have a bit of ownership, or whatever.)
My housekeeper knows I do this, and I also email her all the comments - good and bad. Since I've started doing this I've noticed that they are doing a better job.
One other thing I've done is ask my housekeeper for a list with contact information, of her other clients in my area. She knows I'll have no problem letting them know about the quality of work she does for me.
I'm also thinking about starting a notebook with the cleaning check list that the housekeeper will have to sign and date each time they are there. I'll leave it in a drawer that guests can see.