A text of merely the one symbol, the question mark: ?
Clearly a ruse to get a response from a gullible person and be told they owe money to the IRS or some such B.S.
By the way, the IRS NEVER phones and says you owe money.  You'll get official letters in the real mail, not via phone or email.

just a text from someone I believed to be in the Indian Ocean

Text from a woman believed to live in Sweden.

Received a bad SMS message from this number.

a text from someone stating they were general tony craig .. romance scam involving money