Major Updates About the 3rd Interstellar Comet

Could a passing star (or alien tourist space bus) not give an object a large enough kick to put on a hyperbolic trajectory?

I assume that there is a method to estimate how much mass a comet that large, fast, and probably icy would lose as it passes the sun. Do you have any idea what amount that might be? Would a substantial loss of mass change the speed and trajectory of it?