Unprofessional, Flaky and not worth the time and effort

After finding a house we liked on show we communicated with Sandra that we wanted to make an offer, we followed up with a call to put in an offer, Sandra told us that she would forward the offer to purchase contract. This was followed by radio silence. We tried calling, whatsapping (she was online and read the messages) and smsing to make a formal offer. After a week of not responding, she finally answers the call saying someone had else had come to view the place and the house has already been sold. This is incredibly unprofessional, and we do not feel we were given a fair chance to buy the property. She was flaky and did not give us the chance to make a formal offer with the owners despite our intention to do so (communicated on various platforms). Regardless of whether the new owners had put in better terms and price, we should have been informed. We have never received such an unprofessional experience from any other estate agent we have worked with before,