Final Fantasy VII: Ruby Weapon missing!

Recently, I play Final Fantasy VII (FF7). I follow the walkthrough to play so that I will not miss any important events. However, after I defeated the Ultimate Weapon, according to the walkthrough, I should be able to find Ruby Weapon in the desert of Gold Saucer.

But, I couldn’t meet it. Ruby Weapon is missing! And I tried to find the solutions from internet. Only few people had same problem as mine. Yes, I can meet Emerald Weapon in the sea, but not Ruby Weapon in the desert.

But lastly, I found it, after I have levelled up a lot. I think, the condition to meet Ruby Weapon also depends on the level of the characters.