  A striking feature of the Vela pulsar (PSR J0835$-$4510) is that it undergoes
sudden increases in its spin frequency, known as glitches, with a fractional
amplitude on the order of $10^{-6}$ approximately every 900 days. Glitches of
smaller magnitudes are also known to occur in Vela. Their distribution in both
time and amplitude is less well constrained but equally important for
understanding the physical process underpinning these events. In order to
better understand these small glitches in Vela, an analysis of high-cadence
observations from the Mount Pleasant Observatory is presented. A hidden Markov
model (HMM) is used to search for small, previously undetected glitches across
24 years of observations covering MJD 44929 to MJD 53647. One previously
unknown glitch is detected around MJD 48636 (Jan 15 1992), with fractional
frequency jump $\Delta f/f = (8.19 \pm 0.04) \times 10^{-10}$ and frequency
derivative jump $\Delta\dot{f}/\dot{f} = (2.98 \pm 0.01) \times 10^{-4}$. Two
previously reported small glitches are also confidently re-detected, and
independent estimates of their parameters are reported. Excluding these events,
90% confidence frequentist upper limits on the sizes of missed glitches are
also set, with a median upper limit of $\Delta f^{90\%}/f = 1.35 \times
10^{-9}$. Upper limits of this kind are enabled by the semi-automated and
computationally efficient nature of the HMM, and are crucial to informing
studies which are sensitive to the lower end of the glitch size distribution.
