This is an URL, not a physical file. To make sure the redirect behaves properly, you need to know whether it represents a directory with missing final slash (on the original domain this would be handled by mod_dir) or an extensionless URL.
As your redirects are currently written, case #2 is covered by the rule intended for case #3. Remember that mod_alias (Redirect by that name) reappends the entire rest of the path.
If the requests represent missing directory slashes, they will then get a further redirect on arrival. You may choose to handle them manually if there's been a mistake and you're getting a fair number of requests in this form. But you're not obliged to do anything more about them. There's a longing list of Redirects You Don't Need Unless You Need Them; missing directory slashes are on the list.
If the requests represent extensionless URLs, you'll need more work.
Note that if your file and directory names contain no literal periods-- the hostname and the extension delimiter don't count --you can make the rules simpler and more efficient by using the forms ^[^.]$ and ^[^.]+/$ The second form potentially creates a single server hiccup, but it only involves one character.
Wait, let me save time by responding in advance to the follow-up post: BECAUSE A SINGLE OPTIMIZATION FROM THE SITE OWNER RESULTS IN THOUSANDS OF OPTIMIZATIONS FOR THE SERVER.