Omega symbol polished out

Hello Omega Forums! I recently purchased a birth year ( Reference ST 145.022 78) 1979 Speedy. When I got it the chronograph hand stopped at 140 down by the 25 minute indexes and the whole watch stopped running. I brought it to my local guy before sending it back and he took pictures with his digital magnifying apparatus of the serial number, the movement and the Omega emblem on the crystal to mark sure everything checked out - all did! The correct logo in the hesalite for 78 too! Then I sent it back to the seller- for the issue to be solved. Now I’ve gotten it back and the watch is running brilliantly keeping perfect time. The problem is the logo in the hesalite has seemingly vanished!! Upon noticing I asked if they’d changed the cristal out while repairing the original issue. They told no but they had polished both inside and outside of the crystal as it was scratched! Is this possible? Most likely they broke the original crystal and put an after market one in? Has anyone heard of the Omega symbol being polished out while polishing the interior of the hesalite? And, I’ve been searching like a madman with a loupe, taking pictures and blowing them up ( fingers on phone not prints) and I can’t see it. How hard are the ‘78’s to see with the naked eye and a loupe? Any insight is greatly appreciated.

you have to check from another angel and the logo is (or was) embossed inside

Is it common to polish the crystal inside? To me it makes no sense, how could it get scratched there in the first place?

Based on the photo OP provides, I dare to judge the new crystal is flawless, which raises my doubts whether the crystal wasn't swapped for an aftermarket one - without a logo. I guess a real historical crystal with a correct logo carries some value.