Bugs are rarely occurring because of software itself (hence an app monitoring the blockchain for that is not plausible) but because of humans. With that being said I can assure you that the steemd blockchain is coded at the highest standards and it has functional and unit tests in place. Each version and each release comes with these tests, which are basically ran to maintain the integrity of the software itself between various upgrades.

But the nature of blockchain itself makes it difficult to test it. You may end up with a case in which all the functional and unit tests are passing, but some edge case on the real blockchain will not. In this specific case, the bug was triggered by somebody issuing a vote on the lockout period, which, for some nodes was 12 hours, but for others 12 seconds. To put in practice such a test is really time consuming and really hard to implement. I salute the fact that there is a Steem testnet and, in an ideal world, this bug should have been triggered there. But again, the nature of the blockchain makes it very hard to do so. Testnet doesn't have the same number of witnesses or even the same structure of them.

I am also annoyed about these hiccups, but, as a programmer doing this thing for a living, I know they are inevitable. Sooner or later a big boo-boo will happen. And when it happens, the only thing that matters is how fast and dedicated (and lucid) those involved in fixing it are.

And in this case they did their job very, very well.