Yes, you can see it, if its there, by shining a bright light into that pinhole from the outside, but it's hard to tell if what you are seeing is really the flat plastic seal that is supposed to be there at the very back end, a mm or two inside, or if it is really blocking debris !
You don't want to damage that real seal ! Its all the way through the body at the back, though.
In my case, the misapplied white sealant had pretty nearly filled the pinhole to the outer edge. It came out as a little mm long plug, using a needle and tweezers.YMMV...
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