Since the release of v3.5.1 earlier today we have had several reports of missing phrases. Due to this we are releasing v3.5.1 (build2).
If you already have v3.5.1 installed, simply download the product again and re-upload the new package. Then go into your AdminCP:
Extensions >> Language >> Manage Language Packs
Then for "(MASTER) English (US)" run "Find Missing Phrases".
If you don't have v3.5.1 installed you can run the conventional upgrade routine.