Both of Sauber’s main team figures were missing in action on Thursday as Nico Hulkenberg and Esteban Gutierrez practiced in Monaco.
Roger Benoit, the very well connected correspondent for Swiss newspaper Blick, said it is "very rare" that neither Peter Sauber and team boss Monisha Kaltenborn are present at a grand prix circuit.
"They are somewhere in eastern Europe," he said, "on the sponsor search."
The search for new money is increasingly important this year, as midfield teams prepare for the much more expensive turbo V6 engine rules of 2014.
"It’s hellishly expensive," Red Bull team boss Christian Horner admitted on Thursday, referring to the 2014 rules.
"The timing (of the rule change) probably isn’t ideal for some of the teams further down the grid."
Lotus team owner Gerard Lopez agrees: "The timing is ... I don’t know if it’s well-chosen. It’s certainly odd."