Use of forest floor for movement is seen in Slow loris. Have seen it twice.. But it is not that common though. Any sort of canopy gap caused due to roads, felling might lead to such behavior where the loris has to cross the gap may be in search of a mate or in search of new feeding grounds..
Can only speak about ones in Captivity, however at Blackpool Zoo (UK) they did - but it was generally only because there was no connecting bridge between the two trees - once a rope bridge was installed they didn't come down as far as I am aware.
It the agro-forest environment near Bandung, West Java, they have been observed by researchers travelling on the ground between trees. I would not constitute this as forest floor however. Given an available canopy, they will likely choose not to come down to ground level as it leaves them far more open to aerial predators. If they do cross a gap on ground level they will do so as fast as possible to minimise time spent in the open.