Could be countless reasons from a banned member that knows hacking to a parent that is against steroids and knows hacking or someone that knows hacking. We have also seen on other boards where hackers finds vulnerabilities in a site, exploits them and then contacts the owner to offer "assistance" in safe-guarding your site from future attacks. Essentially using their skills to gain income from the sites they hack.
It happens to every site at one time or another. You just have to make sure that your database is always backed up and that as the attacks happen you continue to implement safe guards until you are able to stay ahead of the hacker(s). If a hacker takes down your site permanently, then you can always change server companies and just reload your database onto that server. Sites that never come back from attacks are due to the owner not following through on backing up their site daily. Even if they would have backed up their site weekly then the most they could ever lose is a weeks worth of content.
As for phone issues, other then when the site goes off line while we deal with implementing new safe guards after the ddos attacks, there shouldn't be any issues there as we have updated tapatalk as well as moving the site to its own dedicated server. So when the site is back online there should be no issues with loading and site functionality?