There is very valuable distinction to be made between lessons learned and lessons identified, a distinction which is made very clear in the lesson learning systems applied in the UK military sector.
The operational units of the UK Ministry of Defence define an identified lesson as learning which has the potential to add value and which needs to be communicated, and recognise that a lesson does not become learned until something changes as a result.
I think we could therefore work with the following definitions
A lesson identified is a recommendation, based on analysed experience (positive or negative), from which others can learn in order to improve their performance on a specific task or objective.
A lesson learned is a change in personal or organisational behaviour, as a result of learning from experience.
Ideally this will be a permanent, institutionalised change, but we know that lessons are not always permanent, and can be unlearned as well as learned, so I will leave the word ‘institutionalised’ out of the definition for the moment.
So if learning a lesson has to involve a change in behaviour, perhaps the change IS the lesson.
So you could say
"I always look over my shoulder before opening the car door - that's a lesson I learned from a cyclist friend".
"We always specify in the contract that our contractors have a demonstrable and effective knowledge management system - that's the lesson we learned from that repeat mistake in Malaysia".
"Since the holiday in Madrid, I always pack my medicines bag in my carry-on baggage. I've learned that lesson!"
Without the change, the lesson has not been learned. Therefore the change is the learned lesson.