The wearbar in many Keystone trailers is not what we'd think of as a "in/out slider" that is positioned along the path that the slide moves when it's being extended/retracted...
On my Cougar and on many other "through the rail slide systems" Keystone used a combination rubber seal/wearbar/guide/mount plastic extrusion. It is screwed to the trailer floor, under the slide, runs from the extreme front of the slide cutout opening to the extreme rear of the cutout opening. If you "get under the partially extended slide, you'll see a rubber seal (quite possibly torn away from its mount) that rubs against the DARCO underliner. Use your fingers, pull that rubber seal down and shine a flashlight into the space. You'll see a black plastic "bump" about 2" in from the rubber seal. The slide bottom "rides on that bump" which is the actual 'wearbar'.....
Here's a couple of links to photos of this "plastic combination extrusion"
https://www.pinterest.com/pin/443675000772580510/
https://www.trekwood.com/products/11...-Bar-168-Black
The Pinterest photo is "upside down". When you compare the two photos, you'll see that the rubber seal is "on the top in the Trekwood link" which is t he way it's installed on your trailer. The slide "rides across (not along) that bump".....