It's does happen from time to time: https://blockchain.info/orphaned-blocks

Orphaned blocks happen because of how the Bitcoin network reaches consensus on the blockchain. Because there is no central storage for it, every Bitcoin client stores its own version. It can be the case that a majority of nodes have one version of blockchain, but then a smaller minority have another, with two more fresh blocks. After the majority notices that it no longer has the longest blockchain, it will switch to the other one. This can happen when two miners produce blocks at similar times.

Note that blocks only contain transaction IDs. No money is lost during this blockchain reorganization*, because the transactions that were in the orphaned block will be nevertheless included in subsequent blocks.

*actually, the 25 BTC reward from the orphaned block is lost, so the mining power of miners was wasted in that case.