The caterpillar probably wasn't 'healthy.' It had what appeared to be at least four parasitic eggs attached to the head and body as seen in the images. Close-up detail of these is shown in following sighting 4519229.
I see a dorsal pattern of paired verrucae, but no parasites except the triangular yellow thing on one side. @TimL : was that attached.? I see no red dorsal organs, so probably Lithosiini. Please can you take it into protective custody to rear to an adult moth for identification?
The yellow triangular thing is a blossom emerging from its displaced casing. There are four white parasite eggs visible on the caterpillar, two being on top of and to the left side of the head in the final image. The parasite eggs are also shown in closer detail in following sighting 4519229.