Cats have a unbeliveable memory, just this weekend one of our friends cats completely freaked out for apparently no reason whilst the owner was carrying it past a large stand that was holding rosettes......after some disscussions someone remembered that the year before in the very same show hall and in the very same ring that particular stand collasped very close to the same cat!
Unbelieveable but obviously the cat remembered it happening!
I'm sure Bert will get over his experience given time and provided he doesn't catch sight of any stray/feral socks in the near future.
I think its important not to make a big deal of scary situations involving cats, for instance if during a fight between your cats you always seem to favor the weaker rather than the aggressor......you are then appearing to confirm to your weaker cat that something bad has happened and that they should be dubious of that situation arising again.
By this I'm not saying don't intervene during fights or potentially harmful/frightening situations, just do it without making a big deal out of it.......try it out and you'll see after a few minutes all is forgotten!
Sometimes just completely ignoring a cat for a few days will make it come to you for cuddles instead of it running away from you all the time.....The mind and thought process of a feline is very basic once you get to grips with it, try getting hold of a few books on cat behaviour.....its a very interesting subject!