The even numbered panels in the Menin Gate are on your left, the uneven on your right when facing the centre of Ieper (i.o.w. with your back towards the canal). You will find this panel by entering the gate in the middle of the memorial on your right, the stair up and again right, it’s the panel on your right hand side.

In total are 8 VC holders mentioned on the Menin Gate Memorial panels.

On below picture you can see where exactly Warner is mentioned.