  The microquasar GRS~1915+105 is known for its spectacular discrete ejections.
They occur unexpectedly, thus their inception escapes direct observation. It
has been shown that the X-ray flux increases in the hours leading up to a major
ejection. In this article, we consider the serendipitous interferometric
monitoring of a modest version of a discrete ejection described in Reid et al.
(2014) that would have otherwise escaped detection in daily radio light curves.
The observation begins $\sim 1$ hour after the onset of the ejection, providing
unprecedented accuracy on the estimate of the ejection time. The astrometric
measurements allow us to determine the time of ejection as $\rm{MJD}\,
56436.274^{+0.016}_{-0.013}$, i.e., within a precision of 41 minutes (95\%
confidence). Just like larger flares, we find that the X-ray luminosity
increases in last 2 - 4 hours preceding ejection. Our finite temporal
resolution indicates that this elevated X-ray flux persists within
$21.8^{+22.6}_{-19.1}$ minutes of the ejection with 95\% confidence, the
highest temporal precision of the X-ray - superluminal ejection connection to
date. This observation provides direct evidence that the physics that launches
major flares occurs on smaller scales as well (lower radio flux and shorter
ejection episodes). The observation of a X-ray spike prior to a discrete
ejection, although of very modest amplitude suggests that the process linking
accretion behavior to ejection is general from the smallest scales to high
luminosity major superluminal flares.
