Where is my NEM coin ?!

Hi, I sent my NEM coin to a crypto retailer (Easycrypto) a couple of weeks ago.
When sending it, I definitely put a message ( I even screenshotted). Since then I haven’t been received the money so I contacted them. The retailer emailed me that “as there was no memo sent with this transaction, you did not send these funds to us. Just to be clear, we never received these funds”. but when I checked with https://explorer.nemtool.com/,
the message was encrypted. Is that the reason why they can not see my message and received my coin? Is this my fault or the retailer’s mistake? Now, what should I do??

Can anyone please give me a solution to this situation?

Yes. Encrypted message will be not credited automatically by exchange.
They should be able send you back as doing big exchanges (Binance, Poloniex, Bittrex and so on)