The main risk is bloat. Keep the sheep somewhere where you can keep an eye on it, give it some baking soda if it will take it (our goats will lick it out of a pan if they need it). If her sides look like they are swelling she will need treatment.
Yes this has happened to my goat like a week ago.... he thinks hes a dog so he freeranges around the property and stays at home but the other day i forgot to shut the chicken coop door and i found him in there having a great time in their feeder.... so i took him out, put him in his night stall so he wouldnt get stressed and fed him some lucerne and goat mix (he gets that everynight) by doing this i think it helped push it through his system faster, he was fine the next day..... just maybe feeed them and keep a watchful eye on them and dont stress them to much or more of the pellets will be taken into their systems for energy production...... and mostly goodluck and keep us posted on how they go.....!!!