  We analyze relevant signals expected at the LHC for a stop as the lightest
supersymmetric particle (LSP). The discussion is carried out in the framework
of the $\mu\nu$SSM, where the presence of $R$-parity violating couplings
involving right-handed neutrinos solves the $\mu$-problem and reproduces
neutrino data. The stops are pair produced at the LHC, decaying with displaced
vertices to a lepton and a bottom quark or a neutrino and a top quark. We
compare the predictions of this scenario with ATLAS and CMS searches for
long-lived particles. To analyze the parameter space we sample the $\mu\nu$SSM
for a stop LSP using a likelihood data-driven method, and paying special
attention to reproduce the current experimental data on neutrino and Higgs
physics, as well as flavor observables. Our results translate into a lower
limit on the mass of the left (right) stop LSP of 1068 GeV (1341 GeV),
corresponding to a decay length of 1.86 mm (6.61 mm).
