Is it the slip yoke that goes to the rear axle?
It shouldn't hurt anything being off. You can pick them up in the "help" section of the local autostore.
I just checked it looks like a boot where the front drive shaft connects to the transfer case. Weird, I took pics and it was there a few months ago. During that time there was some dealer work for the exhaust y pipe and a transmission mount. This boot is in close proximity of the transmission mount but I can't imagine how that would be damaged during the replacement of the mount. You can see the new transmission mount in the bottom pic its to the right.