When undoing the function “Remove DC offset” Cubase erases the audio in the respective audio event. There is no other way to retrieve the audio than removing the file from the project and reimporting it. The audio file itself on the hard drive is still intact.
This is a major issue as it renders the DC offset function basically useless. It has been reported here more than a year ago but the issue report forum is now closed: Steinberg Forums
This issue exists independently of project sample rate, type of audio file (wav or aif) and 32 or 64 bit versions of Cubase. I have version 7.5.4.
I think it’s a bit weird that something as grave as this still hasn’t been addressed.