How do these companies really know where their data and the data of their customers is really stored? what precautions are being taken?

By doing a daily routine of feedback at the end of the day.

Explanation:

Also it is better to have all data storage in another device other than the feedback device.

ιт ιѕ ωнєи ѕσмєσиє ρυтѕ ιи α ¢σ∂є σя ѕσмєтнιиg тнαт вяιиgѕ α νιяυѕ, σя мєѕѕєѕ уσυя gαмє υρ, σя αℓℓσωѕ тнєм тσ ¢нєαт.

αи∂ уєѕ ι нανє вєєи нα¢кє∂ вєfσяє(ιт αιит fυи)

нσρє ι ¢συℓ∂ нєℓρ уσυ.