R3 pickoff attempt from F2

[Brent]

I'm in position C while F2 throws to F5 attempting to pickoff R3. The throw beats R3, but with F5 having his back to me with his body between R3 and me I see no tag. I call R3 safe. Between innings I ask my more experienced partner if I should have asked him for help on the tag before I made the call. He said no, it's my call and if I didn't see a tag I made the right call. Opinions?