Sigma doesn't leak any of your personal info, nor does it share any of your account data. There's about a 50/50 chance that your account was gained either by having a shit password that got easily brute forced, or you got a virus/keylogger from another sus program you downloaded. If it was an alt, it was most likely sold as a Hypixel ranked SFA or as just an unchecked normal SFA. Oh and for next time, don't blame a 5 year old Hypixel client for your shit security measures 
Also happy to see the Jigsaw rename dev in the replys