You cannot store more than you receive, so yes, any extra resources you obtain via looting is wasted after you raid a player.
In this scenario, you also will not be able to collect resources from the collectors in question and they will instead accumulate in your collector's own storage (every collector has some storage).
This holds true for gold, elixir and dark elixir alike. If your collectors' storage are full, they will not produce any more resources until the resource is collected.
Similarly, extra resources obtained from war bonuses will also get lost if your clan castle storage is full at the time of receiving, so it is wise to collect your clan castle resources before a war ends if it is full or if the loot you receive will exceed the resource capacity of the clan castle.