Yes, the 777 TOGA system is very similar to 737. It is possible to only half press, or miss, the TOGA button which doesn't then engage the A/T. Some pilots have a habit of immediately taking their hand off the thrust lever and pulling back with 2 hands without checking the thrust levers have advanced. The other pilot could be on the radio. You could get a positive rate momentarily, before the speed decay results in a loss of altitude.