Two new 100$ 1929

I just want to tell you this very funny story that happened to me 10 years. I wanted to get US money and went to the small Caisse Pop (credit union) in the small village where I grew up and asked the teller If I could get US money to make a purchase in US. She told me at the time she would have to order US Bills from the main branch because they don't keep a lot US money. She told me she will look in the vault if she still have US money in stock. I asked for 200$ US dollars. When she came back she said " I have some 1$, 5$, 20$ but not enough to make 200$, and I have two 100$. If you want it, it's yours. " I took the two bills put them in the book I had and went back home. Few weeks after I went to purchase what I wanted and the clerk said to me : We don't take counterfeit bills. I was very surprise because I received them from the bank. Nothing to do. Afterwards I looked the bill and saw 1929 Federal Reserve Bank of Chicago. I didn't know at that time US Money at all, but I knew it was a nice pick up. I exchange them to an old collector. ( I was young and now I know It was not a good trade). The question I have now. How long slept these bills in the vault before being asked. I know the Caisse was founded in 1932?...They were brent new with following numbers!