Friend Safari Pokemon ALWAYS gives out at least 2 perfect ivs for each Pokemon.
This means that FS Pokemon may be caught with 2,3,4,5,or 6 perfect IVs.
But, I never heard of Fs Pokemon giving out 0 ivs in one category.
So, this time, you caught a Pokemon with (unfortually) 0 ivs.
Friend Safari Garentees 2 31 ivs in stats, but it does not garentee 0 ivs( which is good)
Hope I helped! :D