This really, really depends on the state. I'd say, generally, you are not correct with that assumption.
Some states require gas WITH ethanol to be labeled, others only label gas withOUT ethanol.
If I remember correctly, Arkansas is a state that doesn't require labeling gas with ethanol. I'd assume that any gas you pump has it in unless you can confirm otherwise. Oh, and 93 would probably be the least likely to be pure from ethanol, with 91 being more likely (pure 91 + 10% ethanol = 93 octane)
For example, in MN we have:
-stations that are: 87/89/91, all with ethanol (HyVee, some Shell, Holiday, and Speedway come to mind)
-stations that are E-10 87/ E-10 89/ ethanol free 91 (with the 91 being labeled as ethanol-free) (usually Kwik Trip and/or stations near lake areas)
-stations with 87/89/92 or 93, all with ethanol (BP and Fleet Farm come to mind)
(as well as stations like Casey's or independents that may only sell 87)
From the stations I've gotten gas at in Arkansas (Exxon in Hope, Sunoco in Alma and a Murphy Express in Little Rock come to mind), I didn't remember seeing any sticker indicating the presence of ethanol at all. I assumed all of it was 10%; this would be like Minnesota. Stations in Iowa and Nebraska, on the other hand, usually label if the gas does or does not contain ethanol. Oftentimes there you'll see the following: non-ethanol 87, E10 87 (cheapest), and premium with or without ethanol (this is at many Kum and Gos, most HyVee's I've seen, some Casey's, some Shells, etc.) Other stations (e.g. Pilot/Love's, some Phillips 66, many BPs) have E-10 87/ 8-10 89/ usually E-0 91). Notable exceptions are certain stations (Sioux City Murphy USA comes to mind) where the midgrade is actually 91 E-10 and premium is 91 E-10.
The moral of the story: it really depends. Assume it probably has ethanol in it if it's not labeled. Hope that helps!