You must run and correcty interpret NMR data. They will inequivocally tell you what you have in this case

The above is the best way to do it.  Though I think the presence of Cu will cause the 1,4-isomer to form exclusively - at least I have never heard of the 1,5-isomer forming under Cu catalyzed conditions.

If the other methods fail, then just do the cyclo-addition thermally which causes the formation of 1,4- and 1,5-isomers, this will give you an authentic sample to compare to.  If anything you may be able to prove it by isolating and proving the opposite isomer. Best O' Luck.

Take a look at this publication: https://www.researchgate.net/publication/269706468_Functionalizable_Red_Emitting_Calcium_Sensor_Bearing_a_14-triazole_Chelating_Moiety

I used Cu catalyst to obtain 1,4 triazole and a ruthenium complexe to obtain the 1,5 triazole. In my case (check 1H and 13C NMR of componds 8 and 11), the 1H NMR signal of the 1,4 isomer was more shielded than the 1,5 isomer, same for the 13C.

Hope it will help.

Article Functionalizable Red Emitting Calcium Sensor Bearing a 1,4-t...

Though it might be late for you to use this answer, but I would strongly encourage you to go through the publication 'Journal of Organic Chemistry, 2012, 77, 8756' which gives a very nice description for distinction between 1,4 and 1,5 regioisomers based on simple 1D 13C NMR experiments.