Hand feeding

I'm new to chinchillas and am hand feeding a 3 week old. I've hand raised other species before but this little one has me a bit concerned. She's thriving - eating great, active, and pooping, but I haven't seen any urine. I tried stimulating her, lined her cage with paper towels so I could see any urine, but nothing. I've had her for 3 days. Do they still need to be stimulated at 3 weeks?