The pictures in the linked article from yesterday are interesting...
A Heathrow spokeswoman apologised for the disruption. "Earlier today there was a technical issue with the Terminal 2 baggage system which has now been resolved," she said. "Passengers are now able to check-in as normal, but a number of passengers who departed from Terminal 2 earlier today may have travelled without their luggage. We are working closely with airlines to reunite passengers with their luggage as soon as possible. We're sorry there's been disruption to passenger journeys."
BBC - Heathrow Terminal 2 baggage piles up after malfunction