Unrasterize a layer?

[Bongoray]

Hi all,

I've been working on a file where a made a bunch of adjustments to a photo. I then put all of those layers into a group. I then applied the oil paint filter to that group as a smart object. Afterwards I made another change, but photoshop made me rasterize it. Now I can't go back any make any changes to the previous adjustments that I've made. Is there a way to "unrasterize" that group? I can't undo and now I'm kinda stuck.

Thanks!

[Ged_Traynor]

@Bongoray have you check the History panel

[Bongoray]

I did. There's only three things listed which doesn't even make sense.