Quran falls by mistake is a possible thing, because humans make mistakes and Allah surely gave us a soft corner to repent for the sins we commit.
Quran is a book of Allah and every Muslim respects the holy Quran from all of his or her heart and never wants to disrespect it in any way but sometimes, by mistake, it falls down.
What to do if the Quran falls from hand or some place ?
Mufti Menk told in a video, that whenever the Quran falls down, we just need to pick it up, kiss it and pray 2 Rakah Salah to seek forgiveness on the mistake you or someone committed.
What is even more disrespectful than dropping the Quran ?
The biggest disrespect to the Quran is that we kept it enclosed on the shelves and never bother to read it once a month!
The biggest sin then this is that we do not read the real message of the Quran and keep it locked up in the cupboard. Many people memorize the surahs from the Quran and when people ask what is the meaning then, they say that they do not know the meaning.
This is a beautiful lecture by none other than Mufti Menk who cleared all the problems that need to be addressed in this regard.
Got a question? Feel free to ask mufti and get quick answers.