What is the Star/Torx Bolt on the bottom of the manual trans
 

I recently learned its not the drain bolt (although some MTF came out).

Anyone know what it is? Or if I screwed up anything by opening it?

I did exactly the same thing last year. Although a ball bearing goes in there, nothing came out of my car apart from oil. Afterwards my gear changes (cold) were decidedly more notchy. I changes the oil again for some Motul and it was a lot better. I believe that it is only used for gearbox assembly but happy to be proved wrong..

Very helpful!

Shaft detent ball is supposed to be in there. I'm not a MT guru so I looked it up. It's presumably loaded with a spring, so if there's no spring that fell out, the ball likely didn't either. It looks like they have some sort of retainer on the spring in this write up.

https://www.nickslandrover.co.uk/wp-...wivels-025.jpg

https://www.nickslandrover.co.uk/how...-detents-work/

ETA: Looks like ours would just fall out. A little scary because I think this means multiple gears can get engaged at once? I'm wondering if I should open it again and make sure its in there. I drove 2 sessions using gears 1-5 without an issue. But I had the same experience as you. No metal ball. I have a strain on my oil catch thing so I'd definitely see it.

Check my sig line for a link to @fireblaze's manuals. I've never been in that spot so I don't have anything more to offer. Seems odd to have a detent ball with no spring but that's what the IPB and the disassembly procedure specifies. Maybe it's an indexing/lock mechanism to allow only rotation of the shaft.