Ref: the WGL Group tracking system
It relies on each group named in an array having either a wgl radio or one of their party being in a command vehicle.
So, what you could do is run a looping monitoring script, say every minute, 5 minutes or an even slower loop,
The script would
a) check if each group in Wgl_GmGroups had a radio, if so, store the position of the group leader in an array using the "set" command
eg if the group your check is wgl_GmGroups select 3
then set your custom array Tx_Gmpos select 3 to their position
The next time you loop and check this group, if they have no radio, then simply used their last stored position as the setpos location for your searchparty waypoint
PARTIAL CODE SNIPPET_grp = wgl_GmGroups select _a
_pos = getpos leader _grp
if(({secondaryweapon _x in wgl_radios} count units _grp < 1)&&({typeOf(vehicle _x)in wgl_cmdveh}count units _grp< 1)) then {goto "LOSTCOMMS"}
tx_GmPos set [_a,_pos]
goto "START"
#LOSTCOMMS
_searchpos = tx_gmpos select _a