A source told E! that the pair were far from shy: 'Justin rented out Lucky Strike's Luxe room for the celebration.
'Additionally, he was seen kissing and flirting with his on-and-off again girlfriend, Selena Gomez.'
While
the pair avoided putting anything on their social media to hint that
they were together, the birthday boy's girlfriend, Ashley Guin, shared a
sweet picture on Twitter.
It's been a while: Justin Bieber and
Selena Gomez were pictured here back in February 2011 at the Oscars when
they were first dating, and have gone back and forth since
Ashley captioned the image: 'The happiest I've seen him in a while.. #goodcompany #heloveshisfriends #happy20thbabe.'
Clad all in black, Selena makes her feelings for the Baby singer clear, starring adoringly up at him.
The
bowling party comes after Selena and Justin and his friend and his
girlfriend enjoyed a night in Las Vegas, Nevada, for the Floyd
Mayweather boxing match.
While earlier, the previous day, Justin and Selena were seen taking a romantic stroll around the Hard Rock Hotel.
He shows his affection in mysterious ways.
Justin
Bieber posted a flattering photo of what appeared to be his on/off
girlfriend Selena Gomez's skirt-clad derriere to his Instagram page on
Thursday.
The 20-year-old Baby singer shared the enigmatic image after weeks of obvious speculation that their relationship is back on.
What's on your mind? Justin Bieber
posted this photo of a woman's derriere who appeared to be his on/off -
and reportedly now on - girlfriend Selena Gomez on Thursday
In the well framed image, the brunette female who appears to be Selena can be seen standing before a bed of red flowers.
With
her back to the camera, the 22-year-old songstress has her long wavy
tresses flowing around her shoulders in a natural fashion.
She is dressed in a form-fitting body con skirt which hugs her buttocks closely, showing off her contours.
Clearly
happy with the pretty image of the Come & Get It star, Bieber
posted it on his social media profile for his near 22 million followers
to see - and likely interpret that they're together.
Party time: Justin Bieber and Selena
Gomez were spotted kissing and canoodling at Lucky Strike in Hollywood
celebrating Justin's childhood friend Ryan Butler's birthday last week
Justin
may be spending some time indoors editing Instagram photos following a
cliff diving incident that landed him with a burst eardrum on
Wednesday.
He and Selena have hit the headlines recently after they reunited and have been snapped together recently on various dates.
They
were spotted kissing and canoodling at Lucky Strike in Hollywood last
Sunday to celebrate the 20th birthday party of Justin's friend Ryan
Butler.
And apparently, Justin and Selena used the party as a way to indulge their once again back on relationship.
Sneaky: The Baby singer posted a picture on Instagram of what appeared to be his girlfriend in Vegas earlier in September
