[LiquidIce00]

you would do
if (playertouchsme) { toinventory yourkey; }
then to check you would just do
if (yourkey) { whatever; }
like in a door you would put
if (playertouchsme&&yourkey) {
hidelocal;
unset yourkey;
}
and the key of course
if (playertouchsme&&!yourkey) { toinventory yourkey; }