So so predictable. How sad that he thinks he can dismiss you like that, then click his fingers and expect you to go back to him.
Don't judge him by his words, but by his action; cutting off contact from you whilst on holiday is proof he has no vested interest in you. Do not be fooled by his manipulation.
His plans never worked the way he hoped - maybe the girl he has been chatting to hasn't shown him enough interest to boost his ego. Either way, you are his back-up plan. The problem with back up plans is they're second best and do us for now, until what we really want is available to us.
If you were high on his agenda, he would have WANTED to have had contact with you - he wouldn't have needed to have distance from you.
If you meant something to him, you would absolutely NOT have to second guess his feelings for you, because he would make sure you felt like a princess, and that you are a priority in his life.
I'm not even sure I would ignore him, because by ignoring him it's probably on your mind that you're ignoring him and it could cause tension at work. If it was me, I would text back and have a straight conversation, no game playing, and using no emotion - so something like:
"Hi hope you're ok. Hope you both had a lovely holiday. I'm not sure how to say this, but I guess being straight is best. I think you're a lovely guy, but whilst you were away it's given me time to think about what I want, and I've realised that you're not what I'm looking for.
I hope this doesn't cause any awkwardness between us at work - it definitely won't on my part. There's no need to reply to this message as I'm not going to change my mind, but just felt it was best to be straight with you.
Take care x"
It does a few things that message: It gives you closure; it's friendly so helps awkwardness at work, it shows that you value yourself; and you get to walk away with your dignity in tact. It basically says 'sod-off I'm not singing to your tune, I value myself much more than you do.