No worries, wasn't implying your directions weren't great! I thought a sign must have been removed pointing into the field maybe as the one from the main road gives no distance or anything! Found it in the end anyway :)
The missing final sign is a large problem. Two of the greats that come to mind - Knockeen & Gortnavern - have the last sign missing. I'm sure there are others. It's down to the farmers removing them, I'm sure (especially when the gate is wrapped with barbed wire!)
I suppose the best course of action is to notify the local council and hope the do something about it.