This sounds like a reasonable suggestion, however it's not quite as simple as us "knowing" that the object exists as Prompt also has a local cache which could be out of date. I guess the problem could come if the database that needs a refresh has a connection issue or is just over a slow connection and causes SSMS to lock up.
We've just received a UserVoice request
in a similar area related to clearing out filters if the object you are trying to select is currently filtered out. It would be great if you could add this suggestion to UserVoice (either as a new idea or comment to the existing one) as we use it to prioritise what we'll work on next.