2000 C2, FL Knuckle 'crack' or my imagination ?

Good morning everyone. I have a quick question regarding my 'new to me' 2000 C2 Cab. Manual. While trying to sort the dreaded 'rattle croak moan squeak' in my 2000 C2 Manual with 49,100 miles; I ordered new suspension components for the front (starting with least expensive to most). This weekend I set about replacing sway bar end-links and outer tie rods, since they not only absorb a fair amount of wear but also because they're trivial to replace on just jack stands. In the course of triaging the tie-rod ends to diagnose the 'croak clunk' I'll call it, I discovered a very damaged Tie-Rod BJ on the Front Left which further cemented my plan to go ahead and replace most of the front end suspension. However, in the process of wire brushing all of the outer surfaces, I noticed the ball joint on the Left TRE appeared to have struck something. (The ball joint socket itself has been smushed in a little bit, and the bottom of the ball joint clearly hit some road debris or a curb or something.) It's honestly tough to tell if it struck something in the road, or if an errant swing of a ball peen hammer caught the boot and damaged it. In either event, it got replaced. Nothing else appears to be damaged and the coffin arm, tuning fork and brake air deflector show zero signs of a collision so it's peculiar that only that one little part has damage. Strange things happen. However, (and here's where my question comes in). The portion of the knuckle where the tie-rod ball joint connects, is displaying a hairline crack in the lower side of the casting. I cleaned it all up and hit it with some ammonia followed by a UV flashlight, and it doesn't appear it penetrates into the machined flange that the ball joint attaches to. I honestly can't tell if it's a flaw in the casting as in a crack that formed during cooling the casting or if it's a stress fracture. Seems odd you could hit something so hard as to crack a wheel carrier casting; but not further damage the control arms, strut or any of the other connective tissue I have ordered a replacement knuckle (salvaged) since the new knuckles are very cost prohibitive. ($60 serviceable salvaged, vs. $800 shipped for new / reman.) My main question is had anyone every seen this absent a collision ? There are no other telltale signs of a previous front end collision. No overspray on the interior unibody, all of the fender liners appear to be original to the vehicle, etc. Just odd that of all the places a crack would develop, it would be here. Photo of the front left wheel carrier / steering knuckle from a 2000 911 C2 Cab with an obvious crack forming from the bottom of the attachment point for the outer control arm ball joint socket. Vehicle has 49k original miles and was seemingly very well cared for less this minor damage to the front suspension.

On a steel knuckle or upright it is common practice to smack with hammer to release the tre or ball joint. 99% sure this is what someone did here to the aluminum. Of course this is the result when u pound on it. U need the puller to do it properly. Amazon Amazon

I think not a crack but more a casting flaw as left of the crack there's more material than on the right of it. File it flat and test again I think it will yield no traces of a crack. Clever way of checking for a crack, never heard the use of ammoniak for that. Does it light up in UV light just like fluorescent dyes do? ETA: I looked at the photo a bit closer and revise the above: what looked like dirt now looks like a crack. Left and right of the crack I can see the material being level.

It looks like a crack to me. Can you stick something in it, like a toothpick?

Quotes source post: 18853263

Yes, I learned it from my grandfather many moons ago. Ammonia is the chemical in Cat Pee that gives it the Amazing Aromatic :P And yes, it fluoresces under the right wavelength of UV Flashlight.