I also managed to see this, it perhaps helped that being retired I could visit on a quiet day (Thursday). On previous visits I got very short glimpses but this time I saw she was out from some distance away and approached her area slowly avoiding any sudden movements. Result five whole minutes!
Small cats like this can be very shy and elusive which is perhaps why they are not more often kept in zoos. Most people visit on busy days when these nervous, reclusive creatures hide to escape the noise and bustle. I look forward to the Rusty-Spotted Cats going on public display later this year. About as tiny as the Oncilla but more stocky in build.
I'd have described the Rusty-spotted Cat as even *more* gracile than the Oncilla myself - the two cat species in the general size range of the species in question which could be described as "stocky" would be the Sand Cat and the Black-footed Cat. The four species are all of roughly similar size, with the BFC being the shortest and the RSC being the lightest.
Woops, sorry, what the keepers told me about the build of the rusty-spotted, unless I misremembered and they said black-footed. They did say the cat was tiny, very feisty and didn't like being vaccinated at all, which is consistent with what they told me about this species at Banham (where they don't have one at present).
It's certainly rusty-spotted which they have offshow at Hamerton - if you want to see the species in the meantime I recommend you visit Port Lympne, which has both rusty and black-footed.