If it happens again, you'll open the phone, maybe find the problem and fix it, maybe not, but probably break something else. Then you'll open the phone again ... wash, rinse, repeat.
Which is why I say that paying a shop to repair your phone is usually cheaper than repairing it yourself - you only pay for, in this case, a screen repair. If, once you've gotten to the point that you're ready to give up DIY and bring the phone to a shop, you'll find that most shops won't work on phones you've had open, and those that will are going to charge you almost as much as a new phone just to diagnose this one (so that you don't get it back with a problem they missed and blame them for it). They you have to pay for the actual repair work. (It usually end up with you refusing to pay the diagnostic fee, the shop not getting paid and using your phone for spare parts. (If you don't pay for the phone after a certain amount of time, which varies by jurisdiction, it's their phone. It's called a mechanic's lien.) So you lose your phone, they lose money (they had to pay the tech for the hours he spent diagnosing the phone) ... which is why most shops won't do a job like that. Too many spare parts phones already. (At one point I had over 1,000 Nokia screens that I bought from various other shops - for less than $1 each. Getting rid of 8 screens for $5 is better than throwing them out.)