Fuel filter inside the injector?

I've got other threads relating to my current struggles but this question is pretty specific.

I have all my injectors out right now to replace the o-rings. I've noticed one of them is missing an internal part. The top orifice is much larger and appears to be missing, from my research, a filter!

It's a bit alarming that apparently I've been running these injectors for 3 years without this piece. Ugh, I am so freaking close to having this truck back in action and then I noticed this. It must have been missing when I got these injectors back from servicing. There's no way it could have come out into the fuel rail right?

Are these filters easily available? It seems to be a rarely discussed part.

 

I’ve used these no problems.
there are 2 sizes of filters long vs short.
https://www.ebay.com/itm/2646280799...EvxPQSGQEa&var=&widget_ver=artemis&media=COPY