Index and Small Formulas returning #N/A

Hi,

I'm having trouble using the INDEX formula in this worksheet: Vials_Index.xlsx

Basically I want to return the corresponding supplier batch and location for each instance of a certain catalogue number. As there is likely to be more than one instance of each catalogue number on the spreadsheet, I know I can't use a VLOOKUP, so I googled and followed the instructions for setting up an INDEX formula instead. I got this to work perfectly on a simple dummy run (sheet 2), but when I tried it out on the main sheet, all I got was an #N/A value.

I can't work out why this is and I'm not really familiar with INDEX or SMALL at all, and frankly my brain hurts now Can anyone shed some light on this please??