Nusphere 17 build 17016.

Case:
1. Open "Find and Replace" dialog (I guess Ctrl+H or Ctrl+R but I may have set my own hotkeys).
2. Enter anything in "Text to find"
3. Tick on "Regular expressions" checkbox
4. Click "Replace All"
5. Open the dialog again and look for previously searched strings.

The text you have searched does not appear there at the top.

If you uncheck "Regular expressions" - it is remembered
If you click "Ok" instead of "Replace All" - it is remembered
If you open the Search dialog (Ctrl+F) and do the same then both searches by clicking "Ok" and "Mark all" remember it.

Looks like a bug to me and rather frustrating one especially when you figured you got the initial regexp wrong. Unless it was specifically designed in this way.

I tried and didn't reproduce. You need to contact support.