Poop regression

Hi! We have been practicing elimination communication since baby was 7mo, now he is 2 and for a year he has been letting me know when he needed to poop. Over a month ago he was sick with mastoiditis and needed to be admitted to the hospital, when we came back home he was in antibiotics for 2 weeks, and it caused him diarrhea. He could not control it and did poop on his nappy every time. The problem is that he has gotten used to poop in his nappy and won't let me know. He has more freedom now, and I am not on top of him all the time, so I can't see the cues I used to see before. I don't know what to do to get him back on track, what would you do?