Visible crew/equipment: When the red car flips through the truck during first car chase after locating Optimus at the house, the first shot doesn't show anything there, then after the car flips through truck, a camera is shown on the ground, presumably filming but looks like they never used the shot. (00:41:53)
Visible crew/equipment: After Drift transforms into a helicopter, Optimus Prime continues driving through the desert. In the first shot after, a camera truck can be seen reflected in the chrome bumper. (00:53:15)
Visible crew/equipment: In the final battle scene, just after Bumblebee temporarily knocks over Lockdown, Cade shouts "Get out of here, now" and it cuts to Tessa and Shane about to get into a tow truck and Shane telling Tessa to get in. In this shot, the reflection of a crew member, most likely a cameraman can be seen briefly reflected on the door of the tow truck. (02:31:40)

Visible crew/equipment: During the finale battle with Lockdown when Shane is driving the truck, you can see the shadow from the filming Go pro on the wheel of the truck. (02:32:35)
Visible crew/equipment: After Optimus stabs Lockdown and slices him in half with his sword, it cuts to a shot of Tessa witnessing it, and Shane getting out of the tow truck. When the camera pans towards Shane, he shouts "Yeah" and the reflection of a boom mic can be seen on the wing mirror of the tow truck just before the shot cuts. (02:33:20)
Visible crew/equipment: When Lucas parks his Mini Cooper next to the old theatre and steps out, you can see a crew member's reflection in the opened car door.
Visible crew/equipment: During the scene where Cade and the rest are running for their life on the roof of the huge apartment building, when the Decepticons are shooting at them, the long shot of them running shows a few crew members crouching against a wall and a camera and also another crew member crouching down in the brick doorway.






Answer: Optimus was being dramatic when he said it contained their memories. Transformers don't carry their memories in their spark any more than humans carry theirs in their soul.
MasterOfAll