Everything posted has been interesting; indeed learning is generally interesting, but enough philosophy...
Both alani123 and nc50lc mentioned the mempool - a clue.
At the advise of some random post found by searching
mempool.dat, I went to my full node wallet (which continues to just eat up disk space but it's what I started with so...) and typed:
bitcoin-cli getrawmempool true
and before me appeared data, which led to a better understanding and more questions:
The file was 9MB in size and dated 2 days ago so I wasn't sure if that meant that I didn't have the last 2 days of transactions or, as I've seen before, the OS doesn't change the date even through some file has been updated
9MB of transactions that weren't picked up? Seems like a lot. (in JSON format, each transaction took 767 bytes so = approx 11,700 transactions)
I then noted 2 fields in particular:
"time": 1573801222,
"height": 603870,
If this is a transaction that hasn't seen a block yet, why does it have a height.
I didn't know how to translate the date field - help appreciated.
So the questions are:
Does the mempool only contain "unselected" transactions?
If so, why does it have a block height?
What does this date field represent? I'm sure there's an easy way to translate it e.g., some online tool - if anyone knows of one, please let me know.
If this does contain transactions already in the blockchain, which field indicates that it was never selected (or never made its way to the blockchain)?