It is unlikely your lid's seal had anything to do with it.
For one thing, I've been brewing with "open" fermentation for years. My primary consists of an Ale Pail with a sheet of clear Plexiglas just laid over the mouth of the bucket. I have never - not once - experienced an infection with this method.
For another, you had a 48-hour lag time. It is possible that your wort picked up an infection in that time, before the Ringwood had a chance to get moving.
But chances are you're not infected at all. Chances are it's just young, green beer. Give it a couple of weeks to clarify and age and sample it again.