The gaffe was revealed by the tweet bearing the words "via Twitter for iPhone" in its bottom right-hand corner.
Twitter analyst Luca Hammer trawled through 3,200 tweets sent by the Nigeria account and found that more than 10% (331) bore the same revealing message.
The Samsung Nigeria account has now been reinstated, but the offending tweets have been removed from its historical feed.
This is not the first time Mr Brownlee has noticed one firm's products being promoted via those of its rivals.
In September, Mr Brownlee noticed that Bollywood actress Anushka Sharma, who was paid by Google to promote its Pixel 2 phone, sent the tweets via an iPhone app.
Other celebrities using iPhones to promote Samsung's gadgets include actress Gal Gadot and Indian tennis star Sania Mirza.
The most infamous example of this practice took place in Russia when Samsung brand ambassador Ksenia Sobchak was photographed in public and on TV using an Apple iPhone X. Samsung sued her for $1.6m (£1.26m) claiming breach of contract.