Hoai Phuong of the central Quang Tri Province said he invested US$100 in Luna after its price hit $0.00001 Friday night.
"I thought I should try my luck, but I didn’t dare to spend much and I was OK with losing all the money," he said.
The coin was delisted from several exchanges immediately after his purchase.
However, the price rose 10-fold by the next morning. It kept rising until the afternoon when he decided to sell at $0.0005, earning $5,000.
Others shared similar stories on social media of earning thousands of dollars on a wager of a few hundred dollars.
But not everyone was lucky.
Nguyen Thanh of the southern Tra Vinh Province bought 2.5 million Luna tokens on Saturday afternoon at $0.0004.
A day later he sold out after the price dropped to $0.0003, resulting in a $300 loss.
Many experienced traders warn against buying on fear of missing out.
"Luna prices will drop further, and some recent bounces were just a bait," Bang, a trader with five years’ experience and an administrator of a Facebook group on cryptocurrency, said.
"Investors will lose more if they keep buying, because Luna has shown no sign of recovery."
A large number of Vietnamese are investing in Luna, some insiders estimated.
Luna’s crash came as a surprise since it was among the 20 largest cryptocurrencies and many funds invested in it.
After trading at $100 last month it has crashed to near zero now.