It really was. I've never played in goals but I was a wicket-keeper at a pretty reasonable level and this was drilled in to me non-stop. I can't imagine it's any different in football.
I know they're slightly different situations but compare Martin's first goal at the iPro to the free kick. Both hit from a similar distance, from a similar angle into the same corner. The first one was from open play so obviously Martinez doesn't have as much ground to cover but it's hit much harder. Martinez's reactions are sharp and his technique is flawless, he just gets beaten by a cracking hit. Ikeme is just a bit sloppy all round.
I think that at some point between Martinez getting injured and returning, signing him permanently has ceased to be a viable option. If he was going to come back in it would've happened after Preston.