although the interfaces themselves don’t have forms to search specifically by ID or UUID, you can open up a particular observation by ID by requesting a particular URL in your web browser. the web page URL for a particular observation will look something like https://www.inaturalist.org/observations/101719252, where the last part of the URL corresponds with the ID of an observation. so you can just input whatever ID (or UUID) you like in the last part of that URL to get to your observation of interest.
if you’re browsing from your Android or iOS device and have the app installed, when you try to open the URL, that should either open the observation directly in the app or your device should ask you whether you want to open it in the app or your browser. if you can’t remember what the base part of the URL is in the app, you can open any observation, and click on the icon to share the observation, and that should allow you to get a URL link for that observation, which you can then modify.
finally, i want to note that i’m not against your request here. but until it is implemented, what i noted above is the way to open a particular observation by ID.