Hmm... how exactly did that work? After all, you can't use Oval Stones the same way you use Water/Fire/Thunder/Shiny/etc Stones. You gave the Togetic an Oval Stone and then what?
Also, i just tried that and it didn't happen. I tried 3 times. So, i don't know what the deal is.
If this is a real problem though, i guess this could have it's on topic on Troubleshooting.