Look for excessive wall movement.
Most anchors and ties are manufactured with a code limit of free play; distance beyond this dimension deserves attention.
Check around doors and windows for obvious gaps in the wall.
The veneer moves when pressure is applied.
Loading applied to the veneer should not exceed code allowable limits of wall movement or tie deflection.
Check for cracks at corners that show wall movement.
Check for bulges at shelve angles or large wall segments.
Check for fallen panels of brick or stone.
Check for open segments of the wall and probe the cavity.
If the wall is built within standards, a tie should be present within code requirements.
Check for shards of stone at joints that may pop from the veneer.