Photos are not displayed in events/faces/photos but do when magnified

One safe non destructive way of accomplishing this is to follow Terence suggestions “There is another way to make a new Library and preserve a lot more of your Work
Download iPhoto Library Manager and use its rebuild function. This will create a new library based on data in the albumdata.xml file. Not everything will be brought over – no slideshows, books or calendars, for instance – but it should get all your albums and keywords, faces and places back.

Because this process creates an entirely new library and leaves your old one untouched, it is non-destructive, and if you’re not happy with the results you can simply return to your old one.”