What would you have done?

It would depend on how long I had the house.
If I only had it a couple of months, then yeah, I would likely say something. If I've been in the house for a couple of years, then no, I own the $45K as well as the problems that the house has.
Having said that, I was confronted with such a situation. My Grandfathers wife was a devote Mormon. Keeping with their teachings, she kept a great deal of cash and food in the house. After Grandpa died, we moved her to a assisted living apartment complex. We packed up everything and put it into storage. When she passed, we asked her family what they wanted us to do with her things. They went through it all, took what they wanted and left the rest.
There was some clothes left that we were going to donate to Goodwill. My wife, being diligent, went thru the clothes and found nearly $112K in the pockets of several coats.
Here we were, her family had the opportunity to go thru the clothes, but chose not to and basically left us a mess. Her estate was quite wealthy and the $112K wouldn't be missed.
In the end, I did call the family, the oldest son beat a path down to my door. He then went through everything again and tore the house apart looking for any more.
My wife and I got nothing, to include a thank you.
We also had to take the ransacked clothes to goodwill.
I just didn't want to explain to my Grandpa why I kept money that I knew didn't belong to me when I die.