I've had the "camping in my office" experience. It wasn't the IRS, but the Florida BPR (Bureau of Professional Regulation).
I was working with a very experienced mortgage broker (he'd been in business since 1950, passed away some years ago), and we got an application for $8,000 for a roof replacement on an elderly lady's house. Normally that would go to a bank for a personal loan, but her credit was non-existent. (What was the line in the movie "I have a very bad feeling about this"?)
Her grandkids were going to do the work and I got "volunteered" to supervise. They had no idea what they were doing, no workman's comp, no liability insurance, no experience, nothing. It was a mess from the get-go.
We'd ask for receipts for the materials, they took offense (Don't you trust us?) and demanded a receipt for their receipt, and so on. Finally, some relative or other got involved and announced that this was done without a building permit and it was OUR fault. The house was in county, and at the time, building permits were not required to replace a roof. The relative got quite snotty about this and reported us to the BPR.
BPR sent an auditor who specialized in auditing cemeteries. He camped in our office for four days and examined every scrap of paper he could lay his hands on related to the $8,000 loan. We got to hear such nuggets as "What you find in wastebaskets is very interesting!" whereupon we started emptying the waste baskets before he got there, when he went out for lunch, and after he left in the evening.
After four solid days of this kind of BS, he announced that he was done and we were off . . . wait for it . . . twenty five whole cents. In the borrower's favor.
My partner held out his hand and asked for the quarter. Auditor left, quietly. That was the last we heard from them.
Oh, yeah, the old lady died during this circus and the house went up for sale.
Best Regards,
Mike/Florida