There are experts at Dataclinic who can deal with phones which have undergone any damage like water damage, fall damage, electrical failure, etc. Any problem that is stopping you from retrieving the data can be solved by the engineers. They are experts at handling any mobile phone brand and have advanced software and hardware for extracting the data in almost any situation.
You may find certain discussions on the net stating that there’s nothing wrong with powering your system down in this manner. But the reality is that they are very much wrong. You should only ever use a hard shutdown in cases of emergency.