Saving BLM boondocking spots

I have been doing my research trying my hardest to fit in the RV community by not being too noisy, filling and dumping appropriately, respecting spaces and all that.

Today, my family and I traveled 200 miles to enjoy our new travel trailer we purchased 2 weeks ago. This is our second trip and wanted to get a head start ahead of 4th of July weekend. We found a one nighter early morning on July 2nd at a national forest which we paid and left then next morning cleaning up for the family that reserved it next.

On July 3rd, we traveled a little further to BLM land to boondock and found a location where clearly spots were being taken. As we traveled further into the land there were quite a few opened spots and being filled quickly.

At approximately 11am, we found a spot but I had one of those outdoor mats on the ground covered in dirt. (I like to reiterate, I have been trying my best to have RV etiquette by reading multiple forums.) Before I unhitched my travel trailer, I googled if leaving a rug out saves a camp site. After my wife and both searched and found nothing, we unhitched and set up camp with outr infant, 14 year old and my mother.

6 hours later, "6"!, an unknown named lady, lets call her Karen came yelling all around my trailer. My wife heads out to greet her but was met with yelling and screaming why we took the spot that had the rug on it. Karen yells at my wife assuming she knew its RV etiquette to not take BLM spots. My wife apologized saying we didn't know. Karen then keeps yelling and saying, "just so you know, people who take spots end up with scratched vehicles the next morning". I was then triggered yet polite and immediately got a short video of the Karen who made a backhanded threat.

Karen continued to throw out names of who she knows and what they were in life as if it means anything for the situation. Karen did the whole, "I'm talking let me finish" and said her daughter had saved that spot at 9am (now 8 hours ago). When I tried to explain that we googled and thought the rug was trash that was left, she refused to hear me out and left.

Am I wrong for taking a spot I that showed no indication of being used or saved? Can a BLM spot be saved? Can it be saved with just a rug that looked like trash? Can I get some insight from the reddit community and how I should approach this the next time I go GLamping.