The 26-year-old overcame a recent knee problem to take part in the Baggies' 2-0 win at Liverpool in the Premier League on Monday night.
"It was great to be back on the pitch and my knee is totally fine now," Mulumbu told the club's official website.
"I am glad to be back and winning again because that shows me I am important for the team, and I hope it will keep going for this team.
"I hope I am the lucky mascot and we will keep playing like this every week."
West Brom return to action next Saturday when they entertain Sunderland in the league.