You did not shear the bolt. The panhard and the mount on the axle will rip apart before you shear the bolt. You didn't lock-tite the bolt when you put it on? Mine loosened up and made banging noises when I didn't put lock-tite on them.
BTW, it is extremely bad to be driving without a panhard. You are basically twisting the joints of the LCA's and UCA's. Very unsafe. Stop driving it until you get the panhard attached.
Also, I would get and use and a Toyota original bolt. The pic of the toytec kit appears to just be a grade 10 metric bolt. I would trust the Toyota bolt before the Grade 10. I am always suspicious when the threads of a bolt are being sheared (like the Toytec bolts are, don't recall if the Toyota threads are, probably are too). I am 100% certain that Toyota has done more testing that Toytec has on to make sure the bolt has had the correct treatment for the application.
part number is 90105-12288, nut is 94622-31200. Should be about $5 for both.
If you end up getting the bracket, then you should probably make some gussets for it and have them welded on, I have read of a guys breaking their brackets off if they didn't gusset them.