Is it safe for a 2 year old to still sleep in a sleeping bag on a mattress on the floor at a day care centre?

There are a number of safety concerns when a baby transfers from a cot to a bed (or mattress on floor)
if the child is wearing a sleeping bag, care needs to be taken to ensure supervision is appropriate to prevent a fall when baby wakes & tries to walk.
Red Nose has this information in (downloadable) Cot to Bed brochure
If a child is wearing a baby sleeping bag whilst sleeping outside of a cot be careful!
A child wearing a baby sleeping bag and not confined to a cot is at a higher risk of falling and being injured. The child must be actively super vised and the sleeping bag removed as soon as the child wakes.
https://rednose.org.au/downloads/RN3356_Cot_Bed_DL_Oct2018_Online.pdf