Yes, you're certainly right. Even with a bunch of light bulbs together, I can imagine if they're not carefully partitioned the light will bounce around off the bulbs to the sides.
But there's another thing I'm trying to remember. Is it possible that at least a small part of what you saw wasn't the display? The eye itself isn't perfect in this regard. Look at any light source in a very high-contrast area----you'll get something you're accustomed to and probably discount. A sort of glare effect. Our eye has a set of coping strategies for dealing with this (moving around, iris dilation), so we become used to "not" seeing it. Sitting in a dark room and looking at the wall next to a bright window will show a kind of fuzzy bleed in. Sorry for thinking out loud...I'll have to see an OLED in person.