I noticed that in 90% of the games I play, whoever wins bot, wins the game. However, lets say my bot lane loses, lets say due to a lucky FB or being forced to back early or burning a summoner during an invade. How do I salvage this situation?
Have a fed rengar.
There are, but it doesn't help at all. When I get behind on ad I just explain to my team that they wont see me until (whatever seems approptate) the 25 minute mark. I hard farm and take gromp / krugs on cd. Try to get back some of the xp that i missed and catch up in gold. Likely their bot lane is in mid by now so i tell the supp to help HOLD NOT FIGHT. Started like 0/4 on vayne the other day and ended up like 10/8 because I was able to get greaves, botrk and shiv at like 26 minutes- which never happens if you start 0/4.
Other options include having champions that no matter what will destroy the other team's adcarry almost instantly 
/ 
for example. Or having a team that split pushes well. 
/ 
can win games that are like 30 kills down.
pretty good especially against ppl like kalista and vayne.
also roaming would help. TP ganks if ur top or only ganking bot and mid if you are jg
I have been telling people about the importance of winning bot for a long time. When you win bot big, you usually have 3 fed players. The ADC, the Supp, and the Jung. It's hard to comeback when 60% of the enemy team is ahead.
In League, it's always really about trading. The enemy team gets a dragon? No problem, just push and get a tower in exchange. Enemy bot lane gets a kill? Perhaps your top laner got a flash out of the enemy top laner and gives your jungler a perfect chance to pull off a successful gank. It's really about matching what your opponent does and making the best out of something bad. The biggest mistake I see people do when they lose lane is literally give up, and troll. If the enemy ADC is, say, 2 kills ahead, you can either farm up in a safer lane that the enemy team is neglecting to complete your build, lane swap with another teammate, or just roam and try to find a few kills here and there. A good time to roam is when you have a bunch of wards around the enemy jungle. Since the junglers are usually underleveled, if you catch them taking a buff and are low on health, you can gang up on him with your support, jungler, midlaner. or toplaner and get a kill off of him. Remember that kills only matter around 35% of the time. 60% of the game is determined by objectives so if your teammates are good at split pushing in lanes farthest from the enemy, you can win the game just by avoiding fighting with the enemy and just quietly taking down towers.
