I just saw your post and question. Not even sure you'll see the answer after all these years, but yes, there indeed was a convenience store on 15th between Robinson and Retallack. It was called 'Joe's'...or 'Joe's Corner Store'...something with that name in it, but we always just called it JOE'S.
I'm in my mid 50's but I have many wonderful memories of walking down to Joe's to buy some candy, ice cream, or pop when I was a little girl. My grandparents lived at 2249 Robinson...so Joe's was just a hop, skip, and a jump away. I'm not sure when it closed down. My grandmother moved away after my grandfather passed in 1985. The last time I visited (to take a walk down memory lane in 2000) I think the corner store may have had already closed down...and I was kind of disappointed. lol
Yeah, the way he designed it with the tree in the way and all, is a little screwy but, it was an awesome store in it's day...and Joe certainly had his fair share of daily customers.