You have just labeled yourself as a careless person in this forum. Your mom put your backup phrase into a garbage can, so it was probably on the floor which is why she was able to sweep it and throw it with the garbage.
Read the OP a little better, because he just showed an example of another member, it's not his story.
Regarding the topic of backups, there are hundreds of similar threads discussing how to achieve the best security and reduce risk to a minimum, but there is no single method that can be considered absolutely safe. One backup is generally a bad idea, but multiple backups in the same location also doesn't make much sense.
Unfortunately, most people cannot afford to keep their backups in different locations, so you have to be innovative and creative. Whatever you do about it, don't talk about it to friends and acquaintances, but also to family members who don't know how to keep their mouths shut.