  In the minimal supersymmetric extension of the Standard Model (MSSM) with
$R$-parity conservation the possibility that the sneutrino and the second
lightest neutralino decay dominantly into invisible channels and, in addition
to the lightest neutralino, carry missing energy, is still open --- both
theoretically and experimentally. It is shown that for a large region of the
parameter space allowed by {\rm LEP-I} data, these particles can contribute
significantly to the process $e^+ e^- \longrightarrow \gamma$ + {\rm nothing}.
This signal, if it exists, can be easily detected at {\rm LEP-II} as an
enhancement over the Standard Model or the conventional MSSM predictions.
