Hi,
Thank you for your query.
You are right, the Win/Lost reason is stored in Opportunity Close activity.
You need to create a view on the Activity table and set Activity Type to Opportunity Close. The reason is stored in the Activity Description column.
Then expand your query to Regarding(Opportunity) to add columns from Opportunity.
Here is how to look for this info in Advanced Find:
- Look for Activity.
- Add filter, Activity Type equals Opportunity Close.
- Add the Description column from the Activity table to see the reason.
.
- Add the Opportunity columns from Regarding Opportunity.

Here is the final query:

Results ( I removed the extra activity columns in the view):

Please note, you cannot go from the Opportunity route to get win/lost reasons, you have to start from Activity. This means the view will be on Activity, instead of Opportunity.
It's better if you create a report (using report wizard) for this purpose.