Odd places you've found phone numbers in your STR?

[Paul Sandhu]

This morning I was checking the plumbing at a house.  The supply line to the toilet was starting to freeze so I put a space heater on it.  I lifted the lid to the tank to check water flow and saw someone had written down a phone number with their finger into the sediment at the bottom of the tank.  What are some of the odd places you've found phone numbers?