[mrtms]

First create a variable like

new bool:reporting[MAX_PLAYERS];

When they do the /report set the:
reporting[playerid] = true;

Add this inside where you want your timer to be at
SetTimerEx("ReportEnabled", 15000, false, "i", playerid);

Then outside
forward ReportEnabled(playerid);
public ReportEnabled(playerid) {
reporting[playerid] = false;
}