Mysterious plastic screw in drain of Bathroom Sink

[damn]

Hello everyone

So I did a blunder at my inlaws, as I was shaving I clogged up the bathroom drain. To remove the stopper I had to unscrew it, it's not one of those popups ( the sink is branded ronbow.) The stopper actually was screwing on a white plastic screw that was attached to a plastic frame sitting on top of the "lifter" (the end part of the mechanism which actually lifts the stopper up and down.)

I've really struggled trying to find a replacement for the screw as I made it go down the drain, mind you I might just be able to get a plastic screw somewhere that fits the frame but...

Anyone got any tips? I've tried searching everywhere online including doing google searches but have been struggling.

 

[SHR]

Retrieve the screw out of the p-trap. If you washed it down the drain, purchase a new drain assembly.