By 60's Trooper, do you mean the pre-Mark 3, old model Trooper E/I frame? If so, the front sights WERE NOT glued on. They were either machined in one piece with the barrel, or later, brazed on. If your sight just flew off, I strongly suspect somebody shortened a barrel and re-attached the ramp.
To reattach it properly, it woulds need to be brazed in place. I recommend sending it in to Colt for this, or buying a new barrel from Gun Parts, and having it fitted.
No glue will hold for long. You could try soft solder sweating it in place, but it probably won't hold long.
In any case, something ain't kosher here, Colt sights don't fly off.