I'm very familiar with the XLSB file format, and it's speed benefits. Of course, this also works against it - because if it were an XLSM file, you might have been able to extract the VBAProject.bin file (which houses the VBA code).
XLSB files are (sometimes) generated by Excel for documents that are open when it crashes - which is why asked, and why I also asked that - if that were the case - what was the original file type... Because when you load a workbook that you then "can't see" (as you described), my immediate thought is that it is an XLAM file for example. That obviously is not the case here though.
Sorry that you weren't able to resolve it, though. I hope that you didn't lose any important code.