I can't say that I have lost access to my bitcoins in past. But this happened with my waves wallet with more than $1k inside it in 2017 and I wasn't able to find the private keys or the backup seed of that wallet. I had to install new operating system in my computer so I did a clean install thinking my wallet was backed up, but in reality it wasn't. So please Everytime you should double check that you have saved your private keys in a safe place.