3 sentences

1. 他走得很急，一转眼就不见了。

   tā zǒu de hěn jí, yī zhuǎn​yǎn jiù bù jiàn le.

   He left in a great hurry and was gone in an instant.

   Source: Dong Chinese Dictionary

2. 他方才还在这里，怎么一转眼就不见了？

   tā fāng​cái hái zài zhè​lǐ, zěn​me yī zhuǎn​yǎn jiù bù jiàn le?

   He was just here a moment ago; how did he disappear so quickly?

   Source: Dong Chinese Dictionary

3. 我的钥匙刚才还在桌上，怎么一转眼就不见了？

   wǒ de yào​shi gāng​cái hái zài zhuō shàng, zěn​me yī zhuǎn​yǎn jiù bù​jiàn le?

   My keys were on the table just a moment ago; how did they disappear in the blink of an eye?

   Source: Dong Chinese Dictionary