Re: Are any neurotransmitters lost in the journey across the synaptic gap?

You are right that there is a gap( we call it cleft) between presynaptic and 
post-synaptic terminals. 

Neurotransmitters have to be removed (As you said "lost". But the neurons 
"lose" neurotransmitters with intention). Because if the released 
transmitters persist at the cleft for a long time, the neuron receiving the 
transmitter signals is excited or inhibited too much. And also a new signal 
cannot get through. As far as we know, there are three ways that the 
transmitters are removed. 1)simply by diffusion; 2)enzymatic degradation. 
This way is mainly used by cholinergic system and the enzyme is 
acetylcholinesterase; 3)re-uptake to presynaptic terminals for re-use. The 
neurons can regenerate those neurotransmitters "lost" by the ways mentioned 
above. 

I hope this information can be an answer to your questions.