i don’t think there’s a bug here.
in the Android app, if you search within your observations, you’re doing a string search.
if you want to do a search for observations by specific fields such as taxon, you should use the Explore screen. select the taxon by clicking the magnifying glass on the screen, and select your own user id by clicking the icon to the right of the magnifying glass.
here’s an example of my own Longhorn Beetle observations in the app:
