How to reproduce:
1. Create a new project
2. Type "is:sprite" in the Project window's search bar and left-click somewhere in the Editor (or type enter).
3. Observe the search bar

Expected result: "is:sprite" is written in the search bar
Actual result: "s:sprite" is written in the search bar

Reproducible with: 2019.4.38f1, 2020.3.34f1, 2021.3.2f1, 2022.1.0f1, 2022.2.0a12, 2023.1

Note: Reproducible with other texts after "is:" too

Note:

This happens because the ProjectBrowser window is matching filters with IndexOf (ex: IndexOf("s:") => which will match is: as well).