Recently, an anomalous vortex behavior was reported on the low-temperature superconducting (sc) phase of U1-xThxBe13 with x=0.0275. At Tc2, the second sc transition, vortex creep is reduced sharply by about three orders of magnitude to undetectable low levels [Phys. Rev. B 65 (2002) 144519]. This lack of creep in the low-temperature phase has been interpreted by Sigrist and Agterberg as due to strongly pinned vortices with fractional flux quanta, trapped in walls separating degenerate superconducting domains [Prog. Theor. Phys. 101 (1999) 965].We present here an investigation of flux creep in UBe13. We then compare these data with previous results from the literature on specific heat and thermal expansion on the same sample, in order to reach a better understanding of the phase diagram of this unconventional superconductor.