Let \(\mathcal {O}_L\) be the ring of integers of a number field L, and let \( f(z)=\sum _{n=1}^{\infty } a_f(n)q^n\in S_k\cap \mathcal {O}_L[[q]] \) be a normalized Hecke eigenform for \(\textrm{SL}_2(\mathbb {Z})\) . We say f is non-ordinary at a prime p if there exists a prime ideal \(\mathfrak {p}\subset \mathcal {O}_L\) above p such that \(a_f(p)\equiv 0 \pmod {\mathfrak {p}}\) . Previous work has shown that f is non-ordinary at p if \((p-1)\mid (k-m)\) for some \(m\in A=\{4, 6, 8, 10, 14\}\) . In this paper, we focus on the case \(m=12\) , which does not belong to the set A. For \((p-1)\mid (k-12)\) , we show that at least one of the following holds: 1. f is non-ordinary at p; 2. \(f\equiv \Delta \pmod {p}\) , where \(\Delta \) denotes the unique normalized cusp form of weight 12 for \(\textrm{SL}_2(\mathbb {Z})\) as usual.