1950s first-edition Superman comic

I lost my 1950s first-edition Superman comic, a real collectors item, yesterday around 3pm near Old Town Plaza in Albuquerque. The cover is blue-green with a bold red Superman title and a DC Comics logo, and the book is in a clear plastic sleeve; the pages have mellow yellowing from age and a small coffee ring on the back. On the inside front page there's a tiny sticker with my initials 'P.P.' and a light pencil note that says 'Panel 7'—these little marks are my only other clues. This book means a lot to me, it was handed down by my grandmother and has sentimental value in my growing collection. If you found it, I’d really appreciate getting it back; I can meet near the Albuquerque Historical Museum or share photos to verify.