Hi Micto!
I am afraid to tell you there is no way to restore the Stream video. Once you snipped and applied it, the unwanted content will be permanently removed. For more details, you can refer to:
https://learn.microsoft.com/en-us/stream/portal-edit-trim
We also recommend you post it in this forum. They're actively answering Streams questions in dedicated forums here.
https://techcommunity.microsoft.com/t5/microsoft-stream-forum/bd-p/StreamForum