Can you post a photo, it would help give an idea. Scraping the bark might not give an accurate answer if the plant is newly dead.
Di the leaves go brown then drop off (or stay on) or did they drop off while still green?
Not sure how long they live but it's a lot longer than 5 years if they're happy.
I can't see much root there.
Pittosprum I think but couldn't say which
I can't claim responsibility DW, you said Thunbergia, by then I was determined to find the answer
Based on your comment DW, try Thunbergia grandiflora variegata.
Got a pickaxe?
Watch out for seedlings, get then while they're still small
I've never seen a vinca with flowers like that
Good point Berghill, all mine are grown from seed.
Though it does look, in one photo, as though the new shoots are from the stump