Yeah neither did I at first... or I'd just as well assume there's a big fat cap hidden somewhere else on the schematic that we're not seeing, since it's just a screenshot.
On that note, if 1.5nF is all that's there, it would be resonant with about 6.7nH at 50MHz. Probably more than that in strays between ground, the shunt resistor, and whatever else is nearby, so that's probably not relevant.
Also, why is 1.5nF from CS to GND? Isn't CS measured relative to VDD? Wouldn't you filter it there..?
Oh and another note: this is a bootstrap configuration, so the IC's ground reference is relative to the negative output. VDD bypass is returned through C15.
Tim