The putschists neglected routine logistics like an absent key general.

Evidence

With typically careless improvidence, for instance, the plotters had neglected to consider that, in Oranie, where General Pouilly was hostile, his deputy, General Lhermitte, on whose support they vitally counted, would be away on leave. — Horne, Alistair, A Savage War of Peace- Algeria 1954-1962, 1348