That one is only present on the left side. #13, the one frame sliders use, is on both the left and right sides.
If you can see the rest of the bolt in there, chances are it sheared at the engine/frame junction. It doesn't look like it pulled threads, unless you cleaned the bolt off before you snapped a pic... usually when you pull threads out of aluminum, you do literally that- the threads come out wrapped in a spiral around the bolt, you end up with a semi-smooth hole, and you need to rethread it larger, or use a Helicoil or Timesert.
Bright side is if it's in there, it might be easy to get out, and it should be easy to make a centering mark. Just get a sharp punch that's a decent fit to the hole, slide it in, and give it a sharp hit or 5. Spray some penetrating lube in first, if it is siezed up, the hammer hits can help work lube into the threads. Then I'd start with a left-handed drill bit. No, I'm not joking. Yes, it's a real thing.

If the threads aren't siezed in the engine side, without the tension of the bolt being tight, odds are once you get a little nibble into it with the drill, it'll start to work itself out, rather than in like a standard bit. I've sheared off weak bolts and used this method, and had the broken bolt come right on out as soon as that bit catches. Start small, 1/8" to 3/16", you can always go bigger if needed, and it lowers chances of messing up those fragile, expensive aluminum threads in the head.
If it doesn't come out with the drill bit, you can try splined bolt extractors. Snap-On calls them "straight bolt extractors", like this:
E1, Extractor, Straight Screw, 1/4"
The depth might not let you use more conventional types of extractors. You might be able to get away with a smaller conventional spiral fluted one, if you're lucky. I hope you are, because my experience with the straight splined ones is that they're not very strong, unless you snap one off, then it'll resist any attempts to drill the now-broken extractor out.
Also, definitely check and re-torque all the frame-to-engine bolts after this, and definitely don't ride until it's fixed. My experience with a shear like that is that it's almost always caused by other bolts holding the same component being loose or broken. If there's 5 bolts and you lose one, you just lost about 20% of the strength, and it just got that much easier to break another one... then you're down about 40%, and so it goes. Used to happen a lot with Humvee 2-piece wheels- there were 12 bolts holding the halves together, and if they weren't torqued right, one would snap. And while it might have taken 4000 miles for that first one to snap, the next one would only take 500, and the next would only take 100.