Did Alex steal the pea purée or just the idea? He's already admitted to having purchased some English peas the night before and making purée takes all of what, 10 minutes? In fact, in his one on one the next day, suddenly he's decided to make pea purée. He should thank Kenny for giving him the idea.
Sure he's a bit of a disorganized crude schmuck but it's not like Ed is perfect either. Don't forget how Ed missed putting a breakfast patty on all the plates back during the Room Service challenge in Epi 3 and totally whiffed on the hollandaise sauce. So maybe Ed forgot or misplaced his own purée.
Interestingly enough, Alex is not the first person Ed questions about taking his purée it's Andrea and then Stephen, who denies knowing anything about it and only then does he ask Alex who says he did not take his purée. All I know is at this point I really stopped caring. I am so jaded about Top Chef that for all we know Padma got hungry and snuck in and had herself a little snack.