With the changes to Spellthiefs edge you will want to get into a habit of backing with them. If your JG is close by though you might be able to hang around (provided you are requesting brief assistance until your adc gets back.)
If both you and the adc are low on hp/mana and your jg is not nearby you may have no choice but to recall and lose some turret plating. While it isn’t really a good thing to lose plating the turrets DO get a little stronger defensively for every plate they lose so it’s not like the enemy team is going to 100-0 the turret in a single recall.
If you have ancient coin and can safely keep the enemy bot lane away from your turret try and get mana coins to get resources back for when your adc returns (coin doesn’t have a tribute penalty, you just won’t see gold coins drop without a nearby ally)
That’s just from my experience, hope it helps!
[sg-lulu]