Happened to my mum!
She said she felt like someone was following her as she kept seeing a new car outside and she didn't know who it belonged to.
My sister who lives with her said she was crazy.
Surprise surprise, few months later she gets a letter with pictures of her sometimes leaving the house saying they did an investigation.
Since the pictures were mostly her limping heavily to take her service dog out to go to the bathroom it was fine.
But yeah its no joke, but makes sense. My mom has been on disability near 10 years, that's 400k+ in benefits paid out. Paying 2k for a private investigator only has to work a small percentage of the time to save money.
Most undocumented immigrants in the US enter legally then never leave.
The idea that most cross the border on foot isn't supported by data.