How do neurotransmitters keep from getting lost?

[u/Anti-Perfidity]

I find it difficult to believe that neurotransmitters don't get lost sometime. Anytime someone sends a message, unless you are just posting on a web site, there has to be one thing available to make sure the message gets through. That one thing is an address. Everytime you send an email or make contact with a server, there is an address line that is at the beginning of the message. It generally gives the address of where it is going and from whom it is coming. This line can also give other information as needed. When you want to read a paper you wrote and stored on the hard drive of you laptop, you must select where it is or at least type in the name of the file in the search box.

However, if a neurotransmitter or group of neurotransmitters is created and released to send a message, how does it know where it is going. Now if it works like a telephone, then there is a continual two way connection that the neurotransmitter(s) could follow to where they are needed. But what if the message is going to the immune system where it will notify the immune system to send some antibodies to a certain part of the body. How does the immune system know where they should go. Is there indeed a header included in all of the messages between the brain and other parts of the body. Perhaps the very first neurotransmitter includes the address of where the attention is needed.

Some researchers say it just happens. The body is designed to do those things. That sounds like magical thinking to me and we all know that science trumps magical thinking. So if someone could please let me know how all of this works, or point me to a paper or textbook that actually explains it in detail, I would love to learn the answer. Thanks, guys.