How to find hidden macros in a VBA project?

I have got an Excelsheet wich was created from my predecessor. My task is to change some details in macros. But I cannot find not one line of code!
When I opened the file the first time I saw a macro, but then I clicked on some other sheets in the VBA and before I got a chance to copy the macro, it disappeared and there is no way I can find it again. I tried to open the file in another computer, but the macro is nowhere to be found.
The file has 50 worksheets and ThisWorkBook. On the "Properties" window for ThisWorkBook I can see that there is a password.

How can I find again the macro?

Thank you for any idea!