Exit out to neighbourhood view (if you are able to) and go into the greek house, if your sim is not there then open the cheat window
Ctrl Shift C and type in
boolprop testingcheatsenabled true hold down the
shift key and
click on a
sim in the house, from the pie menu select
spawn then
tombstone of L&D now click on the tombstone and from the pie menu select get family member and the sims name should be there.
To turn off the debugging tool open the cheat window again and type in
boolprop testingcheatsenabled false and you can sell/delete the tombstone in build/buy mode if you wish
This is only a work around though, it won't stop what is causing the problem in your secret society though, sorry I've no idea what is causing that, perhaps a conflict with your custom content