It doesn't store "sessions", this would constitute a persistence of state between uses, which would provide means for linkability between your various browsing sessions. In other words, it would make you trackable and remove much of the protection Tor Browser provides.
Since it doesn't store sessions, there is nothing to be recovered. There is no (reliable*) way to restore it once it has been closed.
If you're suggesting Tor Browser should write to disk, then you should understand that it is designed not to.
Your suggestion that "there's really no difference between reopening tabs vs opening them for the first time" is false, in this scenario Mallory just puts a unique identifier value, specifically assigned to you, in the website address when you first visit. Then the second time you open it (e.g. the tab is restored) the same value is once again in the website address, so Mallory can confidently link the two sessions (it's either you or someone you shared the link with) and use it as an opportunity to reinsert all the other tracking mechanisms that didn't persist.
If you're not concerned about being anonymous and unlinkable, you can disable this through the
Tor Button (Green Onion) ->
Privacy and Security Settings and unticking
Don't record browsing history or website data however you will not be able to restore the previous session.
You should also note that this makes it possible for a local Mallory, with physical access to the device that Tor Browser is run on, to be able to reconstruct your browsing history.
*unless you want to get into memory forensics and you're lucky and haven't overwritten it in memory with other data since.