Hi everyone, I am pretty new to the Bitcoin & Blockchain world. I am currently reading Mastering Bitcoin, but I have a doubt I can't solve.

Let me use an easy example:

Let's say there are only 2 mining nodes (A and B), which are both mining the block 5 to to add it to the chain.

Now, from what I have understood, the transactions the 2 nodes have in their block 5 can differ. E.g. the transaction "Alice buys a coffee for 5 BTC" can be in the block 5 that the node A is mining, but not in the block 5 that the node B is mining (e.g. because this transaction arrived later to the node B compared to the node A).

Now, if the winning node for this block is the node B, the transaction "Alice...." won't be stamped in the ledger.

When the competition for the block 5 is over, are the "loosing" nodes (in this case the node A) giving up all the transactions in the block they were working on? and take new transaction from the memory pool?

In this case, if the nodes start again mining for the block 6, the transaction "Alice...." will be in the block 6 for node B, but not in the block 6 for node A (node A has given up the transaction from the block 5)

What if node A wins the mining? Won't the transaction "Alice...." be lost forever?

Please correct me

Cheers