A chewed cushion does not prove separation anxiety. The more useful evidence is what happens around departures: persistent vocalizing, frantic escape attempts, pacing, drooling, house-soiling, or destruction focused near doors and windows.
Observe before labeling it
Use a camera for a short ordinary departure and note when the behavior starts, how long it lasts, and whether the dog settles. Do not leave the dog longer just to test the limit.
Do not punish the evidence
Damage or house-soiling discovered after you return is not helped by punishment. It can add fear without changing the emotional response that happened while you were away.
Keep practice below the panic point
For mild cases, practice very short, calm absences the dog can handle and increase slowly. Severe distress often requires an individualized plan from a veterinarian or qualified behavior professional; medication may be part of veterinary treatment for some dogs.
Rule out other causes
Medical problems, incomplete house training, outside noises, barrier frustration, and normal puppy behavior can look similar. A sudden change deserves veterinary attention.