I think the problem is that "pipebomb" isn't a weapon; it is technically a "magazine" for the weapon "put" (an invisible weapon that everybody has). So instead of using 'hasweapon', you may be able to use the "ammo" command:
unit ammo "magazine"
This returns a number; the number of shots in the persons current magazie. So in your case, try putting this in the trigger's condition field:
T1 ammo "pipebomb" > 0
Maybe even try putting "put" instead of "pipebomb". Hope it works