If we look at the level 75 version we have:
DEF:34 HP+19 Enmity+4 "Steal"+5 Enhances "Gilfinder" effect

Then the +1 Version Assassin's Culottes +1
DEF:35 HP+25 Enmity+5 "Steal"+5 Enhances "Gilfinder" effect

Then the +2 Version
DEF:44 STR+5 DEX+5 Accuracy+10 Enmity+6 Enhances "Gilfinder" effect

Steal is missing now.

The reforged version Plunderer's culottes:
DEF:77 HP+22 STR+20 DEX+10 VIT+12 AGI+14 INT+21 MND+13 CHR+9 Accuracy+12 Evasion+17 Magic Evasion+47 "Magic Def. Bonus"+2 Haste+6% Enmity+6 "Gilfinder"+2

The reforged 119 version Plunderer's culottes +1:
DEF:110 HP+47 STR+32 DEX+11 VIT+19 AGI+23 INT+33 MND+20 CHR+14 Accuracy+15 Evasion+38 Magic Evasion+69 "Magic Def. Bonus"+5 Haste+6% Enmity+7 "Gilfinder"+3

Steal never returned. I thought perhaps it was a translation issue, but the same is listed on the legs on the JP version, both the Steal +5 being there and then not being there.

A separate question, aura steal is a very useful job ability and I was looking at ways to maximize it, but so much about steal is currently unknown. Does job level affect it, maybe stats like dex or agi? Is steal +1 meaning 1% of the time you're guaranteed to steal or 1% of the time more than you steal now, you will steal successfully, or something else entirely? Would it be possible to also tell us what gilfinder +3 does and Despoil+ does?

Thank you for your time and wonderful game.