The Scottish champions went into the match knowing they would qualify for the knockout stages only if they got a better result against the Russian club, consigned to the bottom of the table, than the Lisbon club got in the Nou Camp.
In the second half of a tense evening at Celtic Park with the game tied at 1-1 after Gary Hooper's opener had been cancelled out Ari, a roar swept around the stadium which suggested that Barca had scored against the Portuguese club.
However, it was an erroneous call, the game in the Nou Camp finished goalless and had Kris Commons not scored from the spot with 10 minutes remaining after defender Marek Suchy was judged to have barged Georgios Samaras in the box, then it would have been Benfica and not Celtic who had gone through to the knockout stages.
Neil Lennon's men could face Manchester United, Malaga, Juventus, Bayern Munich, Borussia Dortmund, Schalke or Paris St Germain.
Keeper Forster said: "To be honest I thought the other game was 1-0 after the crowd had cheered so I was quite surprised to come off the pitch and find out it was 0-0, but big thanks to Barcelona for doing their job.
"We're delighted to be in the last 16. I think we'll take anyone, we've shown what a tough place it is to come here and we'll fancy our chances.
"I don't know if we're hoping for a really big team or a side we think we can beat, but we'll wait and see and take whoever we get, I'm just delighted to get there.
"The manager was delighted, as was everyone. I think he's really pleased with how the team has developed in the last couple of years and it's obviously a huge thing for the club."