Hibbert pulled back a goal in the 70th minute after the visitors stole into a 2-0 first-half lead through strikes from Gareth Evans and Michael Flynn to secure his fifth goal of the campaign.
Simpson said: "It's the best form he's ever been in. There were lots of positives, unlike the first defeat of the season when we shipped five goals at Dagenham.
"Then there were none, but apart from Hibbert I thought Murray and the full-backs did well so we'll regroup ready for another home game next Saturday.
"But we have to make the home games count. I said before it was an average start to the season. Now it's a bit below average.
"I'm disappointed but after the way we started we should have had a couple of goals and been well in front, but then we gave them a sloppy first goal."