Create Trait/Buff referencing 1st and 2nd Sim

Hi,

I'm creating a trait/buff using S4S where I can reference the first Sim using {0.SimFirstName} or {0.SimName} in my strings table. But when I try to reference the 2nd Sim with whom the interaction happened/caused the buff using {1.SimFirstName} or {1.SimName} I get a an underscore line "___________" in place of the name.

eg. 
{0.SimFirstName} remembering his first kiss with {1.SimFirstName} in my string table results in...

Alex remembering his first kiss with ___________

instead of...

Alex remembering his first kiss with Julia.

Thanks.