Anytime my team can't take and/or hold top, i tend to tell my team to just help bot and defend our mid and bottom from getting back-capped. Reasons for not being able to hold top could be bad team comps, no teamwork, or just bad players or a combination of any of these. It happens to everyone. But alot of games when i see the enemy team rush top and take it , and i know that we have been losing top alot, i tend to help my bot laner take their bot and depending on how good he is, we can defend vs 3 enemies giving us a chance to retake top. One game, Me(Orianna) and a Diana defended vs 3-4 enemies for 250 points straight. It got so bad for the enemy team that they just gave up bot and went somewhere else.
Usually in close games it can be risky to push to their mid when you have top and bot already. Its usually best to just hold or have a coordinated gank in the jungles. I think thats how bot should be treated whenever you can't take top. Bot laner should be helped and it should be treated as if it were top. Obviously the only problem is that its close to the enemy base but it can make for a nice choke point which i have done personally many times.
Screenshot provided so theres no confusion :