The night leading up to it had been otherwise forgettable.
He and his wife watched a series on Netflix, before she went to bed and left him on the sofa messing about on his phone.
Then he received a Twitter notification with news from Elon Musk.
Sebastian told the BBC: "Musk tweeted, 'Dojo 4 Doge?' and I wondered what it meant.
"There was a link to a new event below, so I clicked on it and saw that he was giving away Bitcoin!"
Sebastian followed the link to a professional-looking website where the Bitcoin giveaway looked to be in full swing.
There was a timer counting down, and the website promised participants that they could double their money.
The competition was apparently being run by Elon Musk's Tesla team. It invited people to send anything from 0.1 Bitcoin (worth approximately £4,300) to 20 Bitcoin (approximately £860,000), and the team would send back double the amount.
'Take the maximum'
Sebastian double-checked the verification logo next to Elon Musk's name, and then tried to decide whether to send five or 10 Bitcoin.
"'Take the maximum', I thought, this is definitely real, so I sent 10 Bitcoin."
For the next 20 minutes as the timer wound down, Sebastian waited for the prize to land in his Bitcoin wallet.
From his house in Cologne in Germany he sat there refreshing his screen every 30 seconds.
He saw Mr Musk send a fresh cryptic tweet and felt reassured that the giveaway was real.
But slowly the timer on the website ran down to zero, and Sebastian said: "I realised then that it was a big fake.
"I threw my head on to the sofa cushions and my heart was beating so hard. I thought I'd just thrown away the gamechanger for my family, my early retirement fund and all the upcoming holidays with my kids.
"I went upstairs and sat on the edge of the bed to tell my wife. I woke her up and told her that I'd made a big mistake, a really big mistake."
Sebastian, who asked that the BBC didn't use his real name, didn't sleep that night.
Instead, he spent hours emailing the scammer website and tweeting the fake Elon Musk' Twitter account to try to get some or all of his money back.
However, he eventually began to accept the money was gone forever.
133 miles away in Amsterdam, analysts at Whale Alert had watched in horror as Sebastian's 10 Bitcoin were transferred and then cashed out anonymously a few days later.
The blockchain analysis company has tried to get authorities to take action against the scams for months, but says nothing is being done.
The analysts use a public ledger that shows all movement of cryptocurrencies in real time to spot trends and track money.
They have identified which Bitcoin addresses or wallets are operated by so-called "giveaway scammers" and have tracked the increasing amount of money they are making. Sebastian's 10 Bitcoin was the most they'd ever recorded being lost in one transaction.
Record amounts being stolen
Researchers says scammers are making record-breaking sums in 2021. Giveaway gangs have already made more than $18m (£13m) in the first three months of this year, compared with the $16m made in total for the whole of 2020.
Data also suggests the number of victims this year is set to eclipse previous years. In 2020 around 10,500 people fell for the scams, but already this year researchers say they've tracked 5,600 who have sent money.
Whale Alert founder Frank van Weert says it's hard to say why the scams are not only prevailing, but also becoming more successful.
The criminals' actual techniques haven't changed much since the scams emerged in 2018. They create Twitter accounts that look like those of celebrities such as Elon Musk or billionaire investor Chamath Palihapitiya.
In some cases, like the one that tricked Sebastian, the criminals use stolen accounts of prominent people to ensure they have the blue 'verified' tick to make the account seem more trustworthy.
They wait for the real accounts to tweet, and post a reply to make it look like the celebrities have posted the scams to their millions of followers.
Twitter is a popular platform, but giveaway scams can also be found on YouTube, Facebook and Instagram.