After asking some importants persons , i knew that borrowing full sets to people to get the achievements was allowed.
up2u asked me to borrow him around 35 full sets , that's what i did , then when all the possible-awarded achievements were awarded for him, he sent me everything back.
Yesterday , dodekus asked me to borrow him 3 full sets : Cobra , Copper , and toxic, i sent him those without checking if they were empty , and then he told me that the full toxic set was empty.

It was emtpy before i send it to dodekus (i didn't check before sending) , but i don't know why , because after watching my account history , up2u sent me the full toxic set and all the toxic items that were in.
Did they got deleted by one of you ? or was it a glitch due to the huge ammount of items transferred at one time ? (More than 1500 i think)

(i'm volk23)

Thanks for help.