That would be quite the odd glitch!

...although if the Entei still roamed, then it would in that case remain shiny and you could still catch it. =D

it would be sad if a glitch happened at the start of the game and you found a shiny entei hahaha that would be sad

It hasn't happened to any of my friends or myself but I have heard of it happening before. >_< Ah well, such is life.

that happened to my friend he had just started and saw a shiny and he didnt have any pokeballs he was so anoyed