Locks that work

Frankie, since there is only one 13mm lock recommended, amongst the sea of 16mm/18mm locks, its obvious that you mean the Abus Granit X Plus 54. Abus do a range of locks that are the same size and dimensions, but its the squared bar that truly identifies it as being the 54. Did you manage to see if the bar was square? Otherwise, it might have been one of the similar but less effective locks from the Abus range.

Abus locks from same range as the Granit X 54:
http://www.abus.de/us/main.asp?ScreenLang=us&sid=424602687074737210120101492545124&select=0104b01&ArtikelGrID=1

Or maybe the Abus Ketaro:
http://www.sjscycles.co.uk/product-ABUS-Abus-Ketaro-505--230-mm-D-Lock--Sold-Secure-Silver-Standard-19583.htm

It did look a lot like the 54, but could have possibly been the granit 51, definitely none of the others. The 54 and the 51 have very similiar locking shackles.

But they are both 13mm bars, so why would the square bar shackle be more resistant against cutting? I thought it was just so you couldn't twist the shackle out.