As soon as you realise this make sure to apologise to the chair/meeting arranger, directly if possible rather than email/IM (which should be a last resort). Then get copy of the action minutes and 1) make sure you properly diarise the next session you are invited to and 2) ensure any actions you picked up in absentia are completed on time. Also, try to speak to someone who was at the meeting to get a bit of additional context.