Let's suppose that negative supply shock happened that affected SRAS, but not LRAS. Let's also assume that previously there was long-run equilibrium at point $A$. Due to negative supply shock SRAS decreased, meaning that economy will be either at point $B_1$ (real GDP supplied stayed the same, but price level increased) or at point $B_2$ (price level stayed the same, but real GDP supplied decreased). In both cases they will lead to short-term equilibrium at point $C$
But what will happen next? How will the economy find its long-term equilibrium in this situation? Judguing visually, there are two shortest ways to reach long-term equilibrium after negative supply shock. Either SRAS will increase to its old level or AD will increase so much that long-term equilibrium at point $B_1$ will be reached. But I don't see any reasons why would any of them happen (unless the government intervenes by detaxing/deregulating/subsidizing firms or by spending more). If anything, I would expect AD to decrease due to decreased real wealth (real wealth decreased because both inflation increased and GDP supplied decreased). But such shift wouldn't lead to long-term equilibrium. At the least not without consequent increase of SRAS. But why would such consequent increase happen (assuming no government intervention)?