The picture could be from yesterday for all we know. The bill being two years old has nothing to do with it because I have bills in my packet that are from 95 and 97
Listen garlic, maybe that's the reason why the dad kept it? Because they became rare? People do that. The € got introduced to Germany in 2001 and I know a lot of people who still have old money at home, just because it's not being produced anymore and they wanted to keep it.
Okay I know I'm reviving an old post don't hate me. But as someone who works with money, while they aren't super common those bills do still crop up once in awhile
Also the first line of the picture doesn't really lend itself to your "collectable" theory.