This is because VRChat mangles punctuation characters in user-provided strings before saving them to username/status/bio/etc. Meanwhile, VRChat's own search is unaware of this. This means if you set your username to "Ten.exe" it would be replaced by "Ten․exe", and searches for "Ten.exe" would yield zero results. Confused? That's because the "." in the input strings are U+002E, the full-stop character we know and love from ASCII. But the "․" that was actually saved as your username is U+2024, a lookalike character called "One Dot Leader". VRChat's own search is unable to deal with the character mangling VRChat's backend performs.